There's 2 different "Titan" in Japan, apparently.
To avoid confusion, the "Titan" from CT was renamed Acheron (same monster in FF3, but different palette).

Unfortunately, our Japanese friend decided to name one of the mob in the new CT "Acheron".
So they faced the same problem : it'd be weird to have acheron-monsters while Acheron is supposed to be a general from Allagan army. Thus, they had to rename Acheron.

They could have said they were clone, but it wouldn't have been the case in JP but here, yes. Weird much. You can't have 2 different stories depending on the localization.
Now, from what I got from Ferne's post, I assume the localization team isn't really here to say "what if we said they were clone?" but more "Can we do that? Please? Pretty please?"