Regen braking is a thing for ebikes. I can't speak to OEM ebikes, but check out grin at ebikes.ca. They offer all the parts.

There are some cool features too like setting a speed limit after which Regen activates, so coasting down a hill will recharge you and add resistance to keep you at a safe speed.

The caveat is it doesn't make sense on mid drives because they freewheel when coasting