Just to be clear ... at least in my case, I think it's a mix. I think my WW (who is highly judgmental due to low self-esteem, and anger-prone due to poor impulse control) always found many of my ideas and habits acutely annoying, and, while her mind was in a "let's make it work" mode, she tried really hard to repress those feelings.
But now that she's decided to divorce me, I think it's a relief for her to stop repressing those feelings of judgment and frustration against me, *and* it's ramped up further because it helps her justify wanting to give all that *she knows and remembers* is good in our partnership.
You make a good point. I think that is probably the case in any relationship past the initial days of infatuation and imagined perfection. Everyone is an adjustment when you choose to enter into a relationship with them, and we are all going to have our ways that are going to annoy each other and requiring some tinkering. IMHO, there is really no such thing as that perfect match, or "the one," but rather closer-than-other-approximations, and what-type-of-flaws-can-I-live-with in exchange for someone else offering the same grace to me. It makes perfect sense though, that we become less willing to extend those courtesies when the relationship is on the rocks. I think the differences that also initially attract us to one another can become polarizing with time, as well. For instance, my H is very closed off emotionally, and I'm very open and heart on my sleeve. He loved that about me in the beginning of our relationship, but it was a huge barrier to our ability to communicate and connect as time went on.