I can't see the linked image.

I pulled these from the pdf:

Item No. 1173 - Beef Loin, Porterhouse Steak - The steaks shall be prepared from any IMPS
short loin item. The maximum width of the tenderloin shall be at least 1.25 inches (3.2 cm)
when measured parallel to the length of the back bone.

Item No. 1174 - Beef Loin, T- Bone Steak - The steaks shall be prepared from any IMPS short
loin item. The maximum width of the tenderloin shall be at least ½-inch (13 mm) when
measured parallel to the length of the back bone.

That 1.25" isn't the thickness of the Porterhouse, it's the width of the tenderloin as I mentioned earlier.