They're a little bit pretentious, I'd agree - but handy to see how somebody thinks. (I'd never heard of "2 generals" before - so had a fun "Oh that", "Noo, then that doesn't", "Maybe if I ask on reply?".. nope..)

My guess is that 'impossible problems' either pick up on people who know "Oh that's the 2 generals problem" (gold star) or can quickly cycle through ideas and then pick up on the shortcomings as they mentally explore. Maybe A+ if they can explain why it's impossible, A if they say it is, D- if come up with something that doesn't work.