Motor bikes, ebikes and scooters are not legal to ride on sidewalks, when there is a street next to them, are they?
True, but if pure bicycles are being allowed then it's hard for a cop to tell from a distance if it's an e-bike, they look too similar. So I imagine that many will just operate on footways regardless. They know it's illegal. They just don't care. If it was a scooter then it would be harder to conceal the fact that it's a motorbike. Plus, it would have a number. The e-bike, easy.
When I was young I was hit by an illegal rider in a park and knocked unconscious. It was a hit and run job, which seems to be all too common where footway cycling collisions are concerned. Few years back I was hit when walking home. The cyclist came screaming round a corner and only just failed to stop, his handlebars running into my left arm, but not hard. At first I thought I'd gotten lucky with that one, but on noticing blood dripping found I had a nasty gash on my hand, caused by the brake lever. It was also hit and run.
An elderly man in our street suffered a powerful blow to his back while walking, and was knocked out for some considerable time. He never saw his assailant. He was surprised that nothing had been stolen in spite of his having a fair amount of money on him. I said that a hit-and-run footway cyclist was a likely explanation. We never found out, but it does make sense. A mugger would have taken his valuables, after all. Plus, assailants don't usually strike at the (literal) back of the victim, it being quite hard to down someone that way with a punch or kick.
The EU car design rules disallow anything on the front of a modern car which could worsen the injury of a pedestrian in a collision, for example a sharp hood ornament. Yet, bicycles are exempted from this requirement, and many of the brake lever pivots and so on are brutal objects to strike unprotected flesh with. This in spite of their operating in much closer proximity to vulnerable pedestrians. That makes no sense.
Most of the proper cyclists round here are dead against footway cycling and never do so, but of course that doesn't stop the others.