I mean, a big reason for the low average was the two 1 yard TD plunges.
By standard measures (45+% of yards required on 1st down, 60% on 2nd, 100% on 3rd/4th), Moss had a 100% success rate. He was also the 2nd RB in, the short yardage back and converted every time near the goal-line (also has a 3 yard TD called back).
He may not be the workhorse or primary back, but it’s pretty clear he has a solid role.