They work by inserting a tiny little tab into a tiny little hole in the case and extending a tiny little arm to “lock” it into place. Laptop cases are not particularly heavy duty. I have never tried this but it seems that you could probably leverage the lock and break it out of the hole, even without tools. Someone who really knows what they’re doing could probably do this fast without drawing a lot of attention. If you have bolt cutters and are not visible you could probably just cut the cable and deal with the lock later.
So now you have a hot laptop with the security hole broken. If you’re going to use it yourself, you don’t care. If you’re going to fence it, it will probably look like it’s stolen, but whoever is buying it at a bargain-basement price probably doesn’t care either.