I guess the question is does the UA 777 Hawaii config routinely get subbed in for the 764 that UA flies from EWR. If so, that would be somewhat analogous to what people are complaining about here. On the other hand, if you should up for your LAX-HNL flight scheduled on an AA A321 and ended up on a UA 777 instead, I imagine most people would be pretty happy.

I agree that AA doesn't promise real flat beds on this route so you're taking a gamble when you book on these flights, but at the same time I don't think it's helpful to tell people that they're just wrong for being unhappy when it happens because you happen to have a different preference or because other airlines do something entirely different.