No functionality would be possible because the grade is the current grade
The "Revert to this grade" functionality appears, allowing the user to "revert" the student's "Current" grade, to the current grade. This is pointless functionality because in this case it does nothing. This can confuse the user who may be expecting a task to be performed, when, in fact, nothing will be happening.
With our new Gradebook History feature, reverting is not supported, so hopefully this behavior is resolved. Sorry for the delay in responding to you!