Eh, this is certainly true for a great candidate being able to accomplish anything, but it is even further along to age being a big issue. Having been here now, there is something to the old-dog-new-tricks concerns they have about older folks in UPT; especially in the fighter track. The pressure to perform, put time in, and pick it up quickly is very real in the 38 track and it starts in T6s from day 1. A young candidate is going to be way more moldable, have much more free time to study and focus solely on the program, and just flat out have more brain space available to cram in GK than an older person that has a ton of other life/job/etc. taking up space in there already, in most cases.
I have quite a few points to that I think back it up, but in the vein of brevity (not my strong suit), UPT is a young person's game. Multiple IPs said the same to me in their teaching experience: The old folks seem to struggle in the beginning, but come on strong later when it all starts to get put together.
But, that's not conducive to the T38 track. You've gotta hit the ground running in T6s, catch on quick, and be top-performing from the beginning to give them the confidence you're going to succeed down the road. Of course, if you've been picked up by a fighter unit and have a guaranteed 38 slot, the pressure to earn that slot competing with others is removed, but the pressure to perform perfectly isn't. And that continues throughout fighter career which, again, can be harder for older folks to be okay with.
Again, it's not the case 100% of the time, but it's what .02 is from my short run in this world.