Is that possible that someone breaks the rules and gets suspended x months later because of that mistake?
Yes it is possible. I think everything is possible. When I clicked your thread I thought you were goign to talk about a suggestion to adsense to put banned accounts in a pending mode, so that publishers can still access their account in order to try to see what happened, maybe over 100% CTR as it is the case in click bombings events, so they can then look at their website logs and try to find the culprit in order to make a useful appeal which has chances to get reviewed positively. At the moment when an account is disabled, you can't access it anymore. What would be better is that you can still access it, but nothing else is working, especially ad display on your site. That wouldn't change anything for adsense or the advertizers, but would allow for more fair appeal process, for the honest publishers that is.