I concede, they know when the bike is seized. But what I meant is that they could be unaware when they buy it, or at least claim that.
And if my translation is accurate, this other source also doesn't answer if they alter the bike by getting someone to tune it, or if they were illegal to drive the moment they got their hands on the bike. It claims more than half were modified, but the cited report just says that they were faster than allowed. Bad headline!
Again, you said people buy a lawful vehicle and just know a guy that removes limiters. That is something I have trouble believing. I say, it's far more likely that Amazon will sell a bike that naturally goes faster, like the 20mph ones that are legal right now in California, to anyone, and regions with stricter rules for e-bikes have people who don't know or don't care.
This distinction is important to me, because it shifts the blame from big manufacturers and warehouse corporations who knowingly sell illegal bikes to thousands, to some backyard garage that helped like 6 friends get more power. If the goal is to make our streets safer, going after the thousands will do way more. If truly half of people know someone to remove or remove their limiters themselves, it would be a different story, but all these sources say is that half of used fat bikes are illegal.
Who removed the limiter matters to me, you can think differently, but I'm not budging on this. Your link does claim that it is big business, but admits there are no figures for how many bikes are modified with these kits. Because no one is giving any numbers, I'm the one saying it could be 1 friend installing kits and removing limiters from 6 people in the whole Netherlands.
All I want is the numbers, because until then "people just pay a guy who knows a guy to remove the limiter" just rubs me the wrong way if it might as well be "companies illegally sell limitless bikes anyway".