You're thinking about it from our perspective. We don't know who the character is. We just know the code name. From our perspective, the most likely fit is the character that brave most describes. But imagine it from the developer's point of view. They know the character, and they're coming up with a codename to hide it from dataminers. Say the character is Sora. They can't call it "key" or something. If it's Geno they can't call it "star". It's too obvious. It's not a hint. It's a placeholder name to throw off dataminers. So a general word like brave or hero, which is relatively vague and fits many characters, is perfect because it doesn't point to anyone in particular.
The thing is, while Brave could theoretically apply to anyone, it still has to be a character for whom Brave means something beyond an adjective.
Like, Jack is a generic name, but if you were to pick a codename for Joker, Jack is a really good one (phonetically reminiscent, Joker is the Jack of all Trades, references Jack Frost).
If the character was somebody like Sora, they could go with something like Heart, or Lock, or Nobody (maybe that last one is too obvious).
So for Brave, we can and should narrow it down to characters for whom Brave is a meaningful term (like Bravely Default, Yuri Lowell, and of course, Dragon Quest).