It's measurable biological certainty that reaction times as measured in milliseconds and fine motor control degrade with age. Vision and hearing also degrade. The nature of hands on control of flying a plane means there are no ways to compensate for this.
None of this applies to a politician making decision in a time span of hours, days or months and who can delegate tasks as they wish.
But I think the argument is still valid for other reasons.
Yet Biden (and for some reason not Trump, who's well documented to have the same kind of senior moments but they rarely make it to the news) is raked over the coals for them all the same. Why do we ask the president to be able to walk a stairs, remember pointless ceremony, and all the other things that have nothing to do with performance in office (on which there has been next to zero discussion this cycle)?
I can see that age is a risk factor you don't want for a commander in chief, anymore than you want it in fighter pilots. If so, age limits seem reasonable.