That is incorrect. Guard Reserve students have a MASS score calculated, but it is never used against AD peers for eligibility to track -38s. I think what you may be confusing for policy, was that it was colloquially understood that sponsoring units wanted to see upper-50% relative performance. But none of that is neither written, nor procedural in the tracking of the trainee to phase III.
What does exist, is the discretion for the sq/cc to provide feedback to the sponsoring unit of either (i) non-T38 (frankly very rare) or (ii) non-IFF recommendation (much more common). AD does not pay for the billet, AFRC does (yes, even Guard bureau slots are centrally managed by AFRC now), so it's their [gaining unit] call. In fairness, the sponsoring unit can and usually does concur with the retread recommendation to heavies or bombers. Seen it happen many times, with (ii) being more common in my experience, through 13 years in the AETC TFI AFRC (that's a lot of letters lol) business.
If you performance meets the CTS for T-6s, you will track 38s are a 11f bound Guard/Res guy, regardless of your relative ranking in your class, unless your gaining sq/cc concurs with a non-recommendation from the upt sq/cc.
He is incorrect. AFRC buys the billet, the kid owns the T-38 slot, not AD. When he was sent to UPT, he went in with a centrally funded class allocation for T-38 from the jump. AFRC footprint does not change the AD calculus. I know the whole "different color of money" stumps some people, but AD cats nervous about tracking 38 need not look at their ARCF/ANG classmates as anything but guys who for all competing purposes, are there just "auditing the course". They're not your problem, nor your competition, just like internationals.