EoS Zoro not actually being the strongest swordsman in history (including casual users, connosieurs, heaven-dwellers, Earth-dwellers, doesn't matter) would be unacceptable. He's not fighting for a technical title or "well akkshually" status, he's fighting to be the best. Zoro himself is not one to make excuses about literally anything, let alone haki/swordsmanship/devil fruits/"sword users but not swordsmen". If you have two brain cells paired with a modicum of reading comprehension you can't really deny this if you aren't being disingenuous. So if his status as the world's strongest has a bunch of unaddressed asterisks attached to it, that's going to be a laughable conclusion to the character.
However, if the character has a specific conclusion where he doesn't achieve his goal for one reason or another (e.g. death as a result of self-sacrifice) and those reasons are acknowledged by the story itself, I could see it being fine.