When I shoot my M/L shotgun I always use the same measure for the shot & powder. Can't say as I ever shot a "Square Load" from it though. What I shot was an Equal Volume load. A square load in my particular gun would have fallen about half way between 1 1/8oz & 1 3/16oz. What I normally shot was an even ounce.
The equal volume loading can be used with whatever shot charge you desire, the Square Load is confined to a shot charge which has a column length equal to its diameter & Absolutely /nothing to do with the powder charge, which could be black, bulk or dense smokeless.

Miller/TN
I Didn't Say Everything I Said, Yogi Berra