That doesn't add up the way you think it does. An e-bike is still exercise. In fact, it's pretty good exercise because for general health, time spent doing physical work means more than the actual exertion level of that exercise. For body building, you do need high intensity, but not for general health.

What it adds up to is that e-bike riders tend to get more exercise because the motor lets them go longer distances. What you end up with is transportation and exercise being done together, and the extra calories don't need to be spent on separate exercise time.