One of the biggest problems is actually making sure the information needed is on the poster.
Times, dates, location, pricing, parking etc…
As he points out “it added a bunch of text…” now it’s one all the future designs. That’s great - is the text correct?
To be honest this was a problem before AI. People are not very good at communicating.
This is something I actually cover in the follow-up project's how-to. Ask the AI to sense check the info you've supplied. It can tell you "hey, maybe you should mention venue address".
https://john.hartnup.uk/poster-prompts/how-to-use/
But as with all of it, it's no use if you don't ask the right questions.