strangely People For Bikes and the states define classes by motor performance which seems totally contradictory to something defined to not be a motor vehicle.
This is where legal terms get interesting, since they have their own meaning defined by laws, not the dictionary. So the legal definition can and will vary from the common definition, and are more focused on creating categories and including/excluding things from those categories. Reading through HR727, this is really a bill that creates the category of e-bike, and defines how it interacts with other existing categories when it comes to safety standards.
For example, here's the bit you are referring to, which covers the "not a motor vehicle" portion of the bill, emphasis mine:
For purposes of motor vehicle safety standards issued and enforced pursuant to chapter 301 of title 49, United States Code, a low-speed electric bicycle (as defined in section 38(b) of the Consumer Product Safety Act) shall not be considered a motor vehicle as defined by section 30102(6) of title 49, United States Code
This specifically excludes e-bikes from motor vehicle safety standards, by excluding e-bikes from a specific legal definition of motor vehicle. It doesn't attempt to remove the motor from consideration when it comes to regulating this category. This category cannot be defined without talking about the motor performance and behavior.
The rest of the bill covers creating the category of "Low-speed Electric Bicycles". An interesting bit here is the definition they set in subsection (b), again emphasis mine:
the term ‘low-speed electric bicycle’ means a two- or three-wheeled vehicle with fully operable pedals and an electric motor of less than 750 watts (1 h.p.), whose maximum speed on a paved level surface, when powered solely by such a motor while ridden by an operator who weighs 170 pounds, is less than 20 mph.
The interesting bits here are in bold, since the definition as it relates to speed is clearly focused on the full motor assist, and not pedal assist. But I'll get back to why it's interesting in a second. First, I want to point out that subsection (d) states that it supersedes State law or requirement that "is more stringent than the Federal law or requirements referred to in subsection (a)". Subsection (a) states that e-bikes are subject to specific regulations and that they are considered consumer products. The fact that it doesn't also reference subsection (b) is interesting, and suggests that there's no specific requirement that states adopt the exact same legal definition (but don't quote me on that, as I am not a lawyer). Oddly enough it's not even clear that subsection (d) applies to the motor vehicle safety standards section from my reading.
That said, this does create a rough framework for states to build on, and it does behove states to not stray too far from this. But this bill says precisely nothing about regulating usage. It's simply omitted, so it is left up to state and local jurisdictions by the nature that there is no federal law saying anything on that subject.
However, getting back to the bolded bits, really the only definition here is that the motor output cannot exceed 750W and the motor acting alone cannot push an "average" rider past 20mph. I find this interesting because it shows that People for Bikes did use this definition as their starting point of the 3-class laws they've encouraged states to adopt. Specifically when class 2 (bikes with throttles) is capped at 20mph, but class 3 accounts for faster bikes without a throttle which is allowed under the federal definition. A hypothetical "class 4" could technically exist under the federal definition which could go 28mph with assist and has a throttle, but it would have to cap the throttle at 20mph to stay within the federal definition. I do find it interesting that Class 3 caps out at 28mph instead of simply letting the 750W limit take effect. But using maximum assist speeds is easier for a buyer to understand than wattage output.
And really what People for Bikes is doing is subdividing the category of e-bike into three sub-categories for the purposes of regulating usage locally. All three classes of e-bikes as far as I am aware are still part of this "Low-speed Electric Bicycle" category. But by splitting things up this way, it does allow a jurisdiction to decide permitted usage more granularly. WA state parks apparently decided class 1/3 are allowed on bike trails, but class 2 aren't (pedal assist permitted, but not throttle), but WA in general allows class 1/2 on MUPs which generally have 15mph speed limits, but not class 3 (permission by speed). So there's some advantage to this system if your intent is to regulate based on sub-category. But there's nothing stopping a jurisdiction from saying all three classes are permitted to be used for X/Y/Z.
You can disagree with the categorizations, or how they are applied by the jurisdiction. I can even be convinced that the 3-class system leaves out viable e-bikes under the federal definition, such as that hypothetical "class 4" from above. However, I'm not convinced they are in violation of the definition created by HR727, and instead am more convinced that People for Bikes is aiming to provide a more detailed framework of sub-categories for state and local jurisdictions to work with in the absence of clear federal guidelines, using language that's easier for the public at large to parse, and that they benefit from pushing them nation-wide to avoid a patchwork of different frameworks being used.
all the lawyers I've talked to can't give an opinion without being paid and if you pay them for an opinion they tell you what you want to hear so they are of no help
I'd point out that the exact bounds of a law tend to be figured out in court when judges set precedent, so trying to get a discrete legal opinion is going to be hard. The DMCA is near 20 years old and lawyers are still bogged down and unclear on the side effects of that thing. Partly because few are willing to go to court to be the first ones to find out. So lawyers being cagey on laws that haven't had a lot of precedent set doesn't surprise me.
EDIT: I'd probably add that the 3-class system exists partly to give local legislators more tools to balance the competing demands from constituents. At least with what I've been seeing around eMTB in my area, there's been push back on e-bike use on MUPs and trails. One thing sub-dividing e-bikes as a category allows for is avoiding blanket bans on e-bikes in this situation by creating a mechanism that allows some compromise to be reached while actual data is collected over time about the impacts.