Well, one of the things to keep in mind about Ivalice is there's a continual theme in all the games that you can't necessarily trust the historical record, and The Way Things Happened != The Way People Think They Happened. Honestly, it's probably the overriding theme of the entire universe; it was the entire point of the original FF Tactics (Ramza being obscured by history and Delita taking credit for everything he did), was arguably the same for Vagrant Story ("Disgraced Riskbreaker Ashley Riot assassinated Duke Bardorba. How and why did he do this?" "Losstarot is an evil terrorist and heretic" etc.), and the less said about FF12 the better (NO ONE really knew the real story behind anything because the Occuria had been manipulating history for their own ends).

In that context, it makes perfect sense that the reality of Mateus doesn't match the mythology of Mateus. Almost nothing in this setting does. :P