So this will be a great way to learn more...what's the difficulty??? you will see the area on the map...
1: It's not something that can be 'turned off' for everyone without extensive modding.
2: People will want a base version, so Meneth will have to pick sides or make two versions. Extra work is not good with his already burdened schedule and propensity for fast updates.
3: Many names are in languages that are no longer in existence in the present form. Since the goal is period-appropriate, that seems odd if only some are capable of being done.
4: Is anyone really going to make cross-translated names for every culture? If just vanilla cultures have only one cross-localization apiece, that's 3,364 separate names. Multiply that by the number of titles you're naming.
5: English as a lingua franca makes an English version capable of broader appeal, and the least amount of conflict. It's not like a person can't individually name the title they want with a .csv file in ten minutes if they
HAVE to have it.
EDIT:
Historical flavor is mod creep??? weird to say that for a Historical strategy game don't you think??? Also it's called P.Balance not vanilla Balance...and I was under the impression people here would care to know about history a bit...
anyway....not a real issue for me and Meneth has the final word about it...
'Historical flavor' is perhaps the wrong for it, and it is mod creep. There are already mods that localize names as a stand-alone, and they are easy for an end-user to modify to taste. As to the "Project vs. Vanilla Balance" claim, I like PB because it is very vanilla, and doesn't include a lot of fluff like CK2+ or TPatT. I play like a macro-political simulator, and could care less about minutiae.
And just because the Byzantines are shown in-game with a native spelling doesn't diminish or make people "learn less" about history. The history stays the same no matter who calls it by what name. But it stands a higher chance of confusing players who are not familiar. Us hardcore history buffs and players are little more capable of digging between the lines to learn this stuff. The average player probably isn't. Compare the general forum to the mod forum for quality comparison, or dig through the average comment thread at the askhistorians subreddit and you'll see what I mean.