These labels aren't really that important anyway. It is certainly not true that pro life = wants Roe v Wade overturned. Polls show only around 25-30% hold that view. And only 15-20% think abortion should be illegal in all cases.
Agreed. I think the shift is mainly due to new laws restricting abortion access, thus causing some people to no longer identify as pro-life because they don't think even further restrictions are needed and some who were pro-life or neutral on the issue now identifying as pro-choice because they think the new restrictions went too far.
To say nothing of the new breed of Republicans who basically think using any kind of birth control whatsoever is akin to baby killing. When did a bunch of American Protestants somehow become pre-Vatican II Catholics?