I've noticed the same thing for sure. I do consider my two horses rescues though, because they both came from situations where they were legitimately mistreated. Kainne was severely underweight, wormy, and just not being cared for at all. He was just tossed in a very small, very crowded area with many more dominant horses and left to fend for himself. But he went through nothing compared to what Buddy went through. We picked him up from his *******/abuser just days before he was going to be shipped off to slaughter. He was not only neglected, but also very severely abused and terrified of everything, particularly people. He has permanent scars all over his hind end and sides from whips, but much deeper scars on his mind. He is a horse that really does have to be treated differently because of the severe abuse he suffered throughout his entire life. No amount of work with him gets him past his fear of whips. This guy is in his upper 20s, it's been really drilled into his mind. But no matter how differently he needs to be handled, he is by no means allowed to misbehave. Allowing a horse to misbehave just because he has had a rough past is never okay. There are ways to correct bad behaviour without laying a hand on him. There is no excuse.
Anyway, I've digressed a bit...having worked with horses who actually WERE rescued, I'm definitely know the feeling of annoyance when people say their horses were rescued just to sound totally cool and compassionate or whatever, just because their horses weren't totally pampered before or because their owners were totally mean and smacked them here and there for acting up, or did something else they disagree with. Totally moronic.