"Do you think I should really push my son now to get some B’s in the subjects he doesn’t like so that he doesn’t look like a grade grubber? Right now, he ruthlessly masters anything put in front of him whether or not he likes it, and naturally gets A+'s. "
No. But he sounds joyless. If he can’t be number one, he’s upset. That’s a horrible, stressful way to live.
And it’s not NECESSARY, either, to live that way to be successful.