I've made any number of misspelling and "the the" fixes (the kind that are somehow only visible a week later 🙄) to items posted in Medium pubs. I don't recall making any title/photo changes.

As I understand it (based on comments from editors) once a story is published, it rapidly declines in promotion by Medium. Thus I've been told, "Thanks for submitting this, but since you already published it under your own name it won't get very much attention on our pub." This makes me suspect that a major change won't necessarily be noticed, unless it's right after posting.