Bill Barron was already playing around Philly in the late 40s/early 50s, so he's probably pre-post-bop. As I hear it, he was always working on his own thing, using changes because that's what there was then.
Obviously he wasn't going to go "all the way" into Cecil's thing, but neither was he going to run away from it either.
I think that for Jackie, the free thing was a mental question more than a musical one. It seems to me that he needed a bigger room for his furniture, not a total remodel.