I'm a big ebike fan. I've ridden our Roadrunner (longtail with rear hub) everywhere for the last 3 years, about 18-20k km. We're just waiting for our new Load 7 to arrive, and totally excited about exploring whole new areas of the city and region. I don't think the maths stacks up though for an ebike riding being the same exercise as a conventional bike. Yes it can be faster, it can be more fun, it can take you further and let you ride more - these in combination can mean you are over a week or set period of time expending more energy than you might if you just owned a conventional bike, but the same ride doesnt expend as much energy.
We're essentially talking a formula something like work = force (speed x time) x distance. Making up some numbers, if your trip is 10km at 20kmph for 30 minutes it equals a set level of work. If you add a motor, speed up the trip (say its now only 15 minutes) even if you put in the exact same energy into the pedals as you normally did, its now only 15 minutes of exercise. As soon as the motor puts energy into the same equation, you're putting less in.
Now usually we add other variables with an ebike and increase these, we increase the distance, we take other routes with more hills we wouln't have otherwise, we do more trips, we carry more stuff... all this changes the formula.
My ebike broke down a month or so ago and I rode my conventional bike into work, same trip I do every day on my eBike, OMG - every muscle hurt the next day. After 3 years riding an ebike my fitness wasn't the same as it was riding a CBike 20km 3 x a week. Its totally better than it would have been if I was just taking the bus though!
Similarly, our motor died one time when we were out with M5 on the back, riding home nearly killed me - I had to get off and walk several times. There is absolutely no way the energy requirements for these trips without a motor was the same as it was with the assist.
Love your bikes, have a lot of fun, ride more, ride further, replace cars, do things you could never have done unassisted and know you're getting health benefits. Don't fool yourself that riding a standard bike doesn't burn more energy on the exact same