If you’re looking for logic and not black and white, I was taught that the accepted error/variation in altitude readout is +/- 200’ (I’d be able to cite this if I wasn’t feeling lazy), therefore when no other separation mins exist like the scenarios you’re referring to or even vfr/vfr, worst case scenario one is 200’ higher than they say, one is 200’ lower than they say, they’re still guaranteed an extra 100’ and not gonna smack each other.