OP posted the vid with no other text so what we gather is he is saying "OKW HT on it's own needs buffing." Suddenly people are comparing it to the US HT which makes no sense. Sure they are both half-tracks but that is the end of it.
TL: DR
Faction Asymmetry
If so then the Flak HT should cost about half as much as the US AA, but they almost cost the same and the Flak HT is significantly worse.
Saying Faction Asymmetry does not mean thread invalid. I guess if Jagdtiger was buffed to 500 range you would say That's OP!!! but then I could say 'faction asymmetry' like you did here. Truth is that it means nothing in terms of actual balance.