It should be a simple refresh or cache issue, because if that file is part of the new commit you just forced push, it will pick up the updated commit message.
In the OP's case, it seems that GitHub main repo page incorrectly refect its first push, while the list of commits did listed the right SH1 (the second push, replacing the first through a git push --force
)
It is a refresh issue at the GitHub repo side.