Short of that it would seem to be possible to simply get the measurements off the existing wheels and frame.
Of course. That was, however, not my point. My point was it is usually not easy to find ready spare wheels for your e-bike.
If you, for instance, own a proper e-MTB, we might assume its wheels belong to some popular standard and you might find a spare wheelset, only adding a proper speed magnet (for 6-bolt or Centerlock brake rotor).
It might not be that easy for a road or gravel e-bike. For instance, most of gravel bike rear hubs are 12x142 mm. Assume your rear hub is Road Boost (12x148 mm) and suddenly you find out you are out of choices and cannot buy the ready wheel you need.
Now, the commuter-like e-bikes such as Gazelle or Specialized Vado/Como come with hubs of less popular standards but the worst is their inner rim width, which is neither MTB nor road/gravel. You simply cannot buy ready wheels in that size as they are not available in the aftermarket!
Assume your rear wheel is equipped with an IGH - you can give up at that moment! Ever thought of a spare wheel set for an IGH e-bike?

(It is totally impractical).