I'm on the side that this is NOT a call. A call is when the whistle is blown. No official can overrule another's calls: violations and fouls. This is just indicating how much to score.
Consider the two points of view:
- I didn't see a foot on the line
- I saw the foot on the line
One is conclusive, one is not. If one official saw the foot on the line, it must be a 2.
I also agree that in general we shouldn't both be seeing this...but there are gray areas of the court (especially on transition).