Basically... update submodules to oasis origin latest branch (per one of the extensive answers here): https://stackoverflow.com/questions/5828324/update-git-submodule-to-latest-commit-on-origin git submodule update --init --recursive --remote
do a check to confirm correct submodule commits (per git doc here):
https://git-scm.com/docs/git-submodule
git submodule foreach 'echo $sm_path git rev-parse HEAD'
Output confirms the schema 2.1 correct commit is pinned: Entering 'stix2validator/schemas-2.0' stix2validator/schemas-2.0 b155093705ab4934ee29e7ba4dc99ed053cd4e7f Entering 'stix2validator/schemas-2.1' stix2validator/schemas-2.1 4d010b385b83e53ea322357783ff3be3da5820fb
Push from local to my repo (fork of Oasis) which then feeds the change to the PR on Oasis. I've updated the comments in the PR to confirm.