Iowa Fox,
Good guess, but the change to two forend studs was actually made in 1991 on both the Super 16 and 21" carbine barrels. On the early barrels ... 10" octagon, bull and VR, 12" bull and VR, all Super 16 and 21" tapered carbine barrels were single stud - yet the Super 14's were 2 stud.
Can't say for sure what TC's thinking was, although I was one of their customers who complained about the single stud carbine barrels 25-30 years ago sometime after I started shooting wildcats on my Contenders. Logically complaints like mine are what they were acting on when they switched to 2-stud forends on the longer barrels, so your guess was spot on. Besides not offering solid support to the barrels (yes we knew all about floating TC barrels long before then), the forend mounting screw also often shot loose and on the handcannons the studs themselves shot loose.
FWIW, even on the 2 stud barrels many, many years ago I started welding the forend studs to the barrels on my handcannons, and using machine grade cap screws to mount furniture on all of my barrels/frames (factory, custom and Pachy forends; all grips and buttstocks).