I would not assume that they also apply to square HSS. The radius and the workable flats are the same for square and rectangular HSS, and in the previous code, effective weld sizes for flare grooves for square HSS and rectangular HSS were the same. The new code now has specific criteria for rectangular HSS because those sections are formed in a manner that may not result in 90 degree angles, and the changes to Table 2.1 reflect the recent acceptable practice of 2t. Also, notes m and n were added to the notes for figures 3.3 and 3.4 in the new code.