I can answer the question: it is. That first game against Oklahoma State could be worth 2-3 seed lines based on that win and the resulting SOS opportunities.
If we lose to them, win a meaningless scrimmage against Chaminade, and then play Tennessee (or whoever), that really limits the quality of our resume. We'd have to go like 26-2 the rest of the way to get a top 2 seed.
I sort of agreed until the last sentence. We still play Ohio State, Georgetown, Syracuse, and whoever else we draw in Maui in addition to Cincinnati, Memphis (they should be a tournament team), SMU, Temple, Houston, etc. Not great teams but squads that can get to the tournament. If we lose only one OOC game and go 15-3 in conference, we'll be in position for a 2 seed or better even with a loss in the ACCT.
Now, that said, you're right, the Oklahoma State game is vital. To the extent that it is a 'must win' is semantics but there is a huge difference between playing UNC and Oregon/Wisconsin and Chaminade and Tennessee.