So reading another article (https://www.heise.de/news/Microsoft-lays-hands-on-login-data-Beware-of-the-new-Outlook-9358925.html )makes it more clear. If you consent to syncing IMAP account to outlook then it will transfer IMAP username password and mailserver config to Outlook.

I mean, they could have specified that your IMAP credentials would be synced, but it's redundant considering you're telling it to sync.