Martian, I agree with Mech_Minis here. Their explanation makes sense. Your opposition, actually, does not.
I don't think anyone here disagrees that the position of "Kit Commander" is apocryphal simply because it appears in MW5Clans alone. The position of "Falconer Commander" is canon because it appears in the novels, which are explicitly a canon source where video games are not.
However, both of these positions filled a gap in our knowledge that remained empty before their initial sources were published; "Kit Commander" simply was inferred based on "Falconer Commander"; neither are exactly the same role as "Kit Master" or "Falconer".
Ultimately – and Mech_Minis can correct me on this of course – as far as I can tell, the point has been that this "Kit Commander" title could very, very easily be put into canon material and this would not materially change anything we've already seen in canon except to build upon it. Our windows into the lives of the Smoke Jaguars are quite few and far in between; the idea of a "Kit Commander" in particular simply may never have come up. That doesn't mean that showing one is a contradiction of the canon. There are plenty of ways the
MechWarrior video games have played fast and loose with canon, but this really is not one of them. It's as much a valid fill-in of a gap as any canon source could do if it decided to add more details to an event already written about elsewhere – something that happens a lot, actually; the only difference is it's happening in an explicitly apocryphal product this time.
Even if future canon eventually
does directly address this issue, even if they decide the position of "Kit Commander" is either called something else entirely or specifically does not exist as the Falcons' "Falconer Commander" does, that would not make you retroactively correct; exactly none of us, including yourself or the writers of this video game, would have known that beforehand. For now, it's fair game.
This sort of thing is not just
normal for writing fiction such as
BattleTech, I'd dare to say it's even
expected, whether the material being written is going to be canon or not.