Surely this is just phrased badly, Jake. If this were true, there would be no point to trapezing.



Righting moment is determined by the center of bouyancy (CB) for the boat, combined center of gravity (CG) of everything on it, and the distance between the combined CG and CB (moment arm). Moving the mast to windward (towards the right in this diagram) will move the combined CG right, increasing the moment arm, thus increasing the righting moment - same as trapezing (although the mast/rig will have less effect being lighter than the crew).

Why you would want a sliding mast in a practical boat is beyond me. The complexity is surely not worth it. However, ORMA 60 Tris have used mast canting to good advantage.