It simply isn't true that the only breakage ever in the history of 1Password happened between 7 and 8. As a result, it simply isn't true that you can assume that is the only transition under discussion. You have become hyperfixated on an issue of utter irrelevance to the broader topic.
Bottom line: if your claim is never then you don't get to arbitrarily pick your two comparison points.
Password sync was crippled within 1Password 7 (Google seems to indicate specifically with 1Password 7.8 but I don't personally recall) by way of an automatic iOS app update and removal of the previous version of the desktop browser extension. Subsequently, there were limitations that didn't previously exist on using passwords from Dropbox vaults. If you wanted to continue using that functionality, you were forced to upgrade to a cloud-based vault.
