You're right. The NCAA determines who is in the tournament. According to the NCAA, Pitt is in the NCAA Tournament. This isn't a matter of opinion. OBJECTIVELY, according to the people who hold the tournament - the NCAA - Pitt is in the NCAA Tournament.
And yes... if Pitt were NOT in the NCAA Tournament, then Vegas would not have paid off my bet yet - they'd wait until after tonight's result. The bet is "Pitt to make NCAA Tournament" - as determined by the NCAA Selection Committee.
Pitt already gets 1 tournament share from the NCAA. Same as the other 67 teams. If Pitt wins tonight, they'll get a 2nd tournament share.
The NCAA Tournament has 68 teams... 60 with a bye, and 8 without.
What you're saying is the equivalent of saying last Tuesday's games in Greensboro were not part of the ACC Tournament. The GT/FSU game to decide who got to play Pitt was part of the ACC Tournament. Just as the Pitt/MSU game tonight to decide who gets to play ISU is part of the NCAA tournament.
You're objectively wrong - it isn't a matter of opinion. Anymore than someone who says that unless you make the Sweet 16, you're not in the tournament. That "opinion" would be equally wrong.