See PHI309. There is a window of time between when all builds pass and when Harbormaster actually publishes a revision out of draft.
If any other user tries to interact with the revision during that window, they'll pick up the undraft transaction as a side effect. However, they won't have permission to apply it and will be stopped by a validation error.
Instead, only automatically publish a revision if the actor is the revision author or some system/application user (essentially always Harbormaster).