From what I understand, the only bitcoin that was seized happened when one of the truckers who was gifted 8k (CAD) in bitcoin tried to exchange it for fiat and the ensuing bank deposit was stopped. Other than that, I'm not aware of any being seized.
Discussion
I thought it was a lot more than that, some reports show it was more like 6 btc from Caribou giving up the seed phrases after a search warrant.