It does handle two different size shells, 2 3/4 and 3 inch.
I think the poster misinterpreted that as meaning it took 2 different gauges of shells. Dropping a 20 ga shell in a 12 ga is the most common way of blowing up a shotgun, as it will fall far enough in that a 12 will chamber and fire.
That’s why 20 ga shells are yellow, they used to be the same colors as 12’s.
True if the receiver says so, but that has nothing to do with the choke.