Yes obviously you can’t make every CSS change an option, but changing the main font size is one of the most substantial changes made to a site.
So could you please at the very least edit the release notes to explain the change, give a small rationale, and explain what changes need to be made to revert it. This change should have been mentioned in the first post of the release notes, not the very bottom of the second post with nothing but a link to the pull request.
And the pull request doesn’t even have any description! The commit gives no rationale either. It’s not a pull request that would have passed review if I’d been involved…