I have no idea what the specific requirements for vehicle registration are. I doubt this article is even true, frankly.

But electrifying smaller vehicles is much, much easier than electrifying large vehicles. The biggest cost center in an EV is the battery, and smaller vehicles need proportionally way less battery compared to large vehicles. An ebike that can go 20-30mph runs off of something not substantially different from a cordless tool battery -- a pack of cheap, commodity 18650s -- and otherwise functions off of totally standard, mechanically simple parts.