Your suggestion indeed works. And it may not be the only solution either. I assume having some database queries run periodically to remove revisions from my posts would work too. It would be hacky and needs maintenance with each update but is efficient and non-invasive (a more refined version of this).
It’s in part the simplicity of the solutions that made me wonder if there is an ideological reason Discourse doesn’t let admins disable revisions or delete a post history. If I own the website, at most I get to hide the post history from non-staff users. But I’m not allowed to delete or disable the history. It’s mandatory that the history of my posts be visible to my staff and certainly mandatory that they remain in the database. Unless I nuke the post or resort to hacky ways to manipulate the database.