All of the current 200k bitcoin held by US have not been actually bought because personally I have never seen or read any reports about them purchasing any bitcoin, all what I know and think most people know is that the bitcoin were seized coins from criminals or scams and since then the government have been actually holding them up. This bitcoin has been accustomed as owned by USA but from understanding they haven’t bought any of those, in fact haven’t even been friendly with bitcoin to buy them.
I also think that most of these BTC are seized from suspected criminals. If they start buying BTC, it could had been a big news for the community but little that we know about it except for the session on the approval of Bitcoin reserve from US states.
This current administration is actually the one pushing for a bitcoin strategic reserve which is even yet to be implemented and if they do the begging question is, is it proper under rule of law to have seized assets as national reserve? Shouldn’t they be auctioned?
True, I think it was too early to say that US is buying BTC as Bitcoin Reserve because as far as I know they are still on the process of approving it and majority who had done the process rejects the idea.