wp_save_post_revision( $post_id );
That function will save a revision, combined with add_action( ‘save_post’, ‘FUNCTION ) it could be used to force a revision to save. Though wp_save_post_revision still checks if it should save (if any changes are present) you can filter a positive response using filter “wp_save_post_revision_post_has_changed”.
A complete solution would require some testing, it’s easy to end up with duplicate revisions or other issues.
I found this post when researching a different problem, when I manually make revisions that are essentially a clone of the current post all the ACF fields show in the revision history as changed even though they are not changed.
