Aside from Y pax just being deliberately awkward (a trait not unique to Y), shouldn't the beef be with the airlines who fail to provide adequate facilities in Y, not the Y pax who need to go ?
I agree with you. An earlier poster asked if a business class pax would use the Y loo and I would generally try not to, for this very reason. It isn't fair to the people who have less facilities to share.
As I said earlier, it is not the loo access that worries me, so much as the disruption to my attempts to sleep, when I have paid a substantial premium for more comfortable accomodation.
I took an intra Europe flight, in Y, this week and watched a stream of pax walk from the Y cabin into the C. I was not one of them, but if I'd been in C, I would have been disappointed to suffer habitual distrubance.