The only thing I read about why Dutch gov websites "went down" was as a precautionary measure against this exploit (awaiting the patch), not because they actually got hacked.

Can you link any reports about any site being afflicted by this exploit? (Dutch government website, or other)

But the Dutch government websites do generally (I hope) have users, which is one of the ways the "I need to hit the same php worker, uninterrupted, for about 10 to 30 seconds while absolutely no other traffic hits the site AND I can isolate the one worker from the pool" approach to exploiting fails.

Luck is not a security boundary, they should patch their servers, everyone should. It's not a good thing to have shitty memory management on your server.

However, is this really that exploitable in real world conditions? (no)

So according to you they could have just imposed an upload cap instead and been safe? If all the cybersecurity experts had given useful advice like that earlier in the week people could have been safer and less panicked.