The reason it matters I believe according what Genkai is stating is that it is easier to write characters who are older than kids who are twelve or thirteen. There is a different kind of thought process that occurs in the mind due to age. Are there any huge major changes? Not really. But it is easier to write older characters is what I believe Genkai is saying. An older Sasuke is different from a younger Sasuke by the very nature of being more mature. I'm fully in support of changing their maturity and such if we go for older characters, but I would prefer we keep the relationships as similar to possible to canon just in order that we can all start from the same worldview.

But either way, it seems this is causing an issue. So we will just go with the 12-13 year old ages as if starting in canon. Sorry about that Genkai. I will say that I won't be calling anyone out too much on if they seem slightly more mature or older in the writing due to differing vocabulary or what not.