When my repo got large, I rewrote the history a few weeks back and force-pushed all branches. My local .git directory is now 249 MB but Bitbucket GUI is still reporting it at 789.7 MB and warned me again today while doing git push that I was approaching the 1 GB limit.
I've never used PRs in this repo, so I don't think any of those are sticking to the old commits.
The repo is my private "mymovies" project.