“Could he have been told not to.....to give her credit?”
It may have been a reverse of the usual reluctance for a first officer to countermand a Captain: he was afraid of being thought sexist in taking over control.
Sexism.......no doubt.
That or he figured, "It's now or never. She is supposedly qualified to do this, so let's find out now instead of promoting her upward into situations of more severe consequences."
You can scream until you're blue in the face that someone shouldn't put their hands on a hot stove. You'd be better off encouraging them (if an adult) to put both hands on it.
We're transitioning from decades of infantilization into FAFO and "Steer into the skid."
"You collect the paycheck - you're going to do the job."
"You're a boss babe; you don't need no man."