To be honest I'm totally baffled as how fast passes can generate pages and pages of debate.
Fast passes are, inherently in their design, a tool used to redistribute guests so that lines for rides are more manageable. For that to work properly you need to specify how the redistribution is spread out.
Statistically, in an ideal world each ticket would have one specific time and they would all be spread out throughout the day, but obviously that doesn't create a very pleasant experience.
So what do you do? You pad it out by making it a time window instead of a specific time and you do it in batches instead of single tickets so that families can ride together. You do NOT however make that padded window "From X o'clock until whenever the park closes". That defeats the entire purpose of a fast pass.
I think the common misconception is the assumption that fast passes were founded on the intention of giving guests a way to skip the line when in fact that's a perk that naturally occurs from the actual purpose, which is to subtly tell people when to ride certain rides and spread everyone out. So working off that misconception, they think the "X o'clock to close" rule makes sense since it fulfills the false foundation or they think they're entitled to it because they assume that's the point of the fast pass.
Of course Disney is known for bending over backwards to try and make a guests experience better, so it's entirely logical to conclude that this "unofficial rule" sprang up from cast members making exceptions and word spreading.
Now they're tightening down on the exceptions, most likely because it was getting to the point where it was negating the point of fast passes. That or like someone else suggested, they need more strict data so that they can properly plan this new X-Pass idea.
In any case there is a legit reason behind it. Disneys whole business model is to treat guests as well as they reasonably can in order to acquire a customer for life, so they really wouldn't clamp down on this rule just to piss off people.
As for judging people who took advantage of the lax rules, or calling people who didn't jealous, that's just silly. Some people do what they can get away with and others don't. Neither is universally right or wrong. It's subjective.
It's also reasonable to be a little bummed if the rules are being locked down now. If you have a nice thing and it goes away, you're going to be bummed. It's natural. However it's unreasonable to be flat out angry or to feel entitled to the lax rules just because they used to exist. The rules are up to Disney to decide and as consumers our "say in it" is simply through giving them money or withholding and not going.
Anyway, just my extended two cents.