Proper application for correctable error?

[bainsey]

Let's say A-1 is shooting one free throw. A-2 steps into the lane before the release, but the T doesn't catch it (two man crew), and the free throw is good.

B takes the ensuing the throw-in, and gets to the division line when the new T has a "wait a minute" moment, and blows his whistle. He calls his partner over and quietly discusses whether A-2 stepped in. Definite knowledge is offered, and the new L cancels the basket.

While this is definitely within the time frame of a correctable error, is this a proper application of it? Aren't correctable errors more about what should have been -- or haven't been -- assessed?