This only bugs me because not only did you fail to call the KROSS by it’s actual name (SUPER-V Kriss) or even by BRINKs name, KROSS. Get this straight, the name Vector doesn’t not coexist with the SUPER-V Kriss as seen here:

If Call of Duty started calling the AK-47 a CV-47 (like in Counter-Strike) I suppose you’d start calling it that too right? Sorry, I’m just a gun enthusiast and it’s so juvenile seeing people getting things wrong like that.
I’ll come back to Nechayev’s scarf later, because for now, I don’t recall what it looked like, but I’m pretty sure it’s just some face/mask archetype with a different non-default color.
Why they wouldn’t include an AK let alone the AK-47? Probably because this takes place in 2035, and the AK-47 has been around since 1947.
That’s my guess, just severely old and if they were going to buy weapons for the ARK, and it were built in the United States, it would probably have the latest and greatest weapons distributed to the Security force.