We need to find the exact quote. I don't think Frost ever said he was "the future QB" as if it was guaranteed. I thought he said "he looks like the future at QB" or something to the effect of "his skill set is what we want for our QBs in the future".Frost said out loud that LM was the future QB at Nebraska. There is no vindication here at all. It's ok to be wrong and it's ok to point out that Frost was wrong.
Stop trying to make this out to be something different than it is with your "none of us knows...and that's a fact" and then going right into "this vindicates Coach Frost" as if your prior statement somehow makes your conjecture about the talk with the family real.
We know for a fact that Frost said LM was the future at QB here. We know for a fact that Frost started LM at QB. We know for a fact that LM didn't work out here as a QB and left Louisville after a handful of practices because he couldn't win the starting QB job there either.
Evaluating LM as a QB, saying he's the future QB, and starting him at QB were all mistakes. Again, that's fine, mistakes happen but pretending that somehow those mistakes vindicate Frost because of a "talk with the family" that you invented is disingenuous and borders on a rumor and those aren't allowed here.
I took that quote as being a "public motivator". i.e. a public comment meant to push the player toward a certain goal (whereas coach will be a lot more specific, with a slightly different message, in private).
I don't think that comment in any way reflects poorly on Frost.