This is fascinating. Personally I've actually struggled with enforcing boundaries, but those that are my own rather than those of others. I similarly was often pressured by parents and was even disallowed from having boundaries at all, but that was only one-sided, so I got used to respecting others' boundaries and ignoring my own.

I've communicated this to my roommate, and he's gotten better at making sure that he's not crossing my boundaries (or boundaries I want to have but suck at enforcing lol) just by asking multiple times if it's okay to keep going with something (especially with talking to me while I'm doing something else), and at the end saying "you can say no". I've found that incredibly helpful and validating, and perhaps if you do the same, it could have a similar effect.