No, we are both right. A 13mm combo, non FD+ would be OEXM130B std length which is std length (im saying pretty long by comparison), and OEXM13B which is short. The difference is in the numbers not the letters. The addition of a 0 after the size.
I just checked my OEXM 19 and maybe they had a different numbering system back then in 1975, but it is 6 3/4" long end to end. When placed in my palm, all that sticks out is the open end and the closed end. So that is short. I might still have the Snap-On catalog from back then as well.
I remember paying $79.05 for that OEXM 6 to 19 mm conbination wrench set and my pay per week at the VW dealership as a summer student cleaning new cars and prepping cars for the paint booth was $75 per week. See, hard work and no degree gets you two mint Porsche 911s and a slew of motorcycles.
Hell why buy gold, just buy Snap-On.