get killed against TCU, BYU should host a first round NCAA game at this point. If they are 24 now, I think only a blowout loss would drop them behind 32.

However, the second and third rounds are all at the fields of the 1 seeds and 2 seeds. After the first round is over and the field is down to 32 teams (32 teams eliminated in first round games), then there are 8 groups of 4 and the 4 teams in the quadrant gather at the site of the 1 seed or at the site of the 2 seed.

So for home field advantage it matters to get to top 32. But then after that, no additional home field advantage unless you can get to the top 8. Its not realistic for BYU to get to top 8 even with two more wins to win the big 12 tournament. Could be a slight seeding advantage any time they move up, but that's not the same as home field advantage.