Wow what a little rabbit hole. I think the confusion rightly stems from the missing update to the setting name (educate_until_posts), because, afaik, in PR#400074 it seems to intend that the notice is only shown once, and never again, regardless of any count.
So now the setting no longer means “show the message for the first N posts”, but instead
“Only ever show the education message if the user’s post count is already below this threshold, and even then, show it exactly once.”
@Roman Am I correct to think we should update the copy of this setting?