it's also likely mildly more dangerous than a standard ebike, as ebikes typically overprovision their brakes. A customer putting this on a standard bike (especially a disc brake bike) might have less stopping power than they want on an ebike.
1. someone has a cheap disc brake bike for pleasure rides (mostly in the sun)
2. they get something like this for commuting or whatever
3. now they're on their disc brake bike most days (including when it rains), going faster than they're used to
it's not the end of the world, but it also doesn't seem great