As I have an ebike, and have had since 2011, I have checked this out several times in response to similar threads on a variety of forums
There are a couple of link below to help
Personally I feel that if I am getting out of breath and my leg muscles can feel the strain when I get home - then I must have done something better than sitting on the sofa watching Homes Under the Hammer!!!
To be more serious - I have seen a lot of research - from proper organisations - and most of it comes out of the side of ebikes being good for fitness.
Now clearly they are never going to replace hard core road bikes pelting along a flat road at 30 mph or climbing an Alp - but they go fo rthe concepts that
a) an ebike will allow someone who is not able to ride a normal bike for long - or at all - to get out and pedal. And, although the resistence os not as great the fact that they are getting fresh air and exercise is always good
b) casual ebike users are able to go further and faster and hence get to more, and mor einteresting, places because they can get there is slightly less time and with less effort
c) as using an ebike is less effort people who use them for leisure are more likely to go out on them and hence get more exercise - if less exercise each time
d) they make cycling commuting possible for people that would otherwise use a car due to faster travel without getting as sweaty
In my case I have asthma and on occasions I still have to stop on big hills (OK - big for Widnes which is fairly flat!) and when I start out. On anormal bike I could get worried about getting back home but on my ebike I can increase the pedal assist and get home with less potential trouble.
The motor also means that I can get to local areas that I just would not reach easily on a normal bike - and go far further on the canal networks.
OK - if I was a fit young thing I could do these rides easily anyway - but I am not so the ebike is enabling be to ride my bike far further, faster (a bit) and more often..
You do have to remember that ebike laws vary. In the UK/EU the motor power is quite low and the motor has to cut out when the bike reaches 15.5 mph (it makes sense in kph!) - hence if an ebike rider is riding at anything over 16 mph then they are simply riding a heavy bike at that speed with - potentially - and a bit of extra resistance for forward motion caused by the motor in neutral.
(which is quite funny when I ride along a long flat road and someone passes me and says I am cheating - but I know I was generally going at 17-18 mph the whole way!)
I know some of this is not relavent to the exact question - but it may be useful for others as well
Here are a couple of link to get started
https://www.bikeradar.com/advice/fitness-and-training/electric-bike-fitness/
https://ijbnpa.biomedcentral.com/articles/10.1186/s12966-018-0751-8