I don't know about that that Tira's age doesn't seem right in this game though, she is 17yo in SC3 but here she doesn't look any younger that that, 17yo at least to me in this game, but those are fictional characters again so age and appearance don't really match up (Ivy is one good example too xD) at the very least she isn't 11 in 1585 might be wrong but don't know (by the old time line she was born in 1574).
I'm not sure the age really means anything here anymore, Talim is a kid, not that younger that Amy so it doesn't mean we can't have Amy too, plus Talim for now is the only character to go over 1590 and there is still some room left on the right after 1590 so it is still possible even if the fact she wasn't trained yet was right.
Oh, and if we go by the old timeline Talim was 15 (born in 1576) that means that in 1589-1590 (when she appears in this game) she is only 13-14yo xD