The OCC letter from early-Dec has been re-circulating the last few days and allows banks to engage in "riskless principal" Crypto trades.

This flow differs from a prop desk. In plain English: a bank buys Crypto from Customer A and immediately offsets the position to an LP. The bank technically takes legal ownership for a split second (long enough to complete both legs of the trade) but never holds inventory or assumes price risk.

This is ultimately a broker model - economically they match buyers and sellers but cannot warehouse positions or run a prop book.