I think there is a mismatch in a teacher or adimistrator's traditional model of kids growing math knowledge and what a highly gifted math learner can do. In fact, I'm kinda concerned about this gap in their knowledge. Maybe they shouldn't receive any advancement or salary increase until this gap is addressed. It doesn't matter if they have skills to deal with and effectively teach 99% of the students.
It's possible with some exposure and in context they'll come to understand that other 1% with little to no effort. But just to be safe, it could be better to hold back their careers until they have effective tools in place to deal with all ranges of student abilities.
Actually, it's those gaps that will go farthest in building character for the underchallenged. Being a little unready and scrambling in a couple of areas are going to teach far more valuable life skills than the math content ever will.
