Tokens are frozen "in-place" pending investigation. It differs from how it works with btc, because the government does not have control of the private keys that manage the addresses in question - so they go to Tether who controls the smart contract that manages the transactions of the tokens.
This, in practice, means that the US government controls the mentioned tokens for the moment. What happens with them depends entirely on the outcome of the investigation.
US govt could also create a govt wallet and force usdt to transfer the tokens there I imagine, if they want to proceed with seizure. They'd likely will need some legal framework for this but it's easily doable. Then us govt can auction it off as they like.
This, in practice, means that the US government controls the mentioned tokens for the moment. What happens with them depends entirely on the outcome of the investigation.