Press and hold A+B on the same frame. If no attack comes out, you have activated throw storage. Continue to hold A+B. You can move your character around and they will throw once they enter the throw range, but you lose the ability to guard during this state. It is particularly useful for tick throws. You can do a jump in on block, buffer into throw storage, and not have to worry about timing.
Considering there are a few frames of tick throw protection, the few frames of throw startup, and the fact that reversals are so strong, this bug was actually deemed as not damaging to the game. It was intentionally never fixed. So get used to it!