On my bikes (we have 2), the electronics controlling the motor only allows the motor to run when pedaling with some force.

I guess law enforcement can see if you’re pedaling, if they have one eye open. If accidents happen, they can test equipment to ser if it’s illegaly imported / not approved / tampered with / etc.

As usual, «don’t get caught» works up until a point.

If you want to go fast, just get a motorbike. Why bother tampering with a pedelec?

In practice - no one will. But if you get into an accident(especially if anyone is harmed) you can absolutely be sure that the police will check if your ebike was legal at the time or not. If they find you had a motor more powerful than allowed, or that it could ride without pedalling, you will find yourself in a situation where you caused an accident riding an illegaly modified vehicle - and will most likely be found at fault regardless of anything else. And that's not a good position to be in.

You do know that police officer evidence is typically treated as unquestionable by courts? So if the officer says you were not pedalling, then you have an uphill battle to prove you were.

For example in Berlin everything electric with throtle is baned