> You're supposed to fix the frame to the stand, why are you just attaching the wheel?

Because the "wheel grabber" makes it very hard to lock the frame as well as the wheel. About all that is possible without a long wire (which are generally easy to cut and thus inferior to a D-lock) is to get the lock through the rear triangle. This assumes you're able to get the bike in rear wheel first, of course.

I'd rather find a fence or lamppost over using a wheel grabber. I get that density is a concern in the Netherlands but it probably isn't outside the local convenience store everywhere else.