There is simply no precedent for a 23 win (including 12 league wins) power conference team being left out, so your point isn't particularly earth-shattering. Frankly if they win 4 of their last six it is more likely they are a top 5 seed than they are an NIT team.
As I have explained several times, all "league wins" aren't created equal. This is accentuated by unbalanced (non-RR) league schedules. Conceivably, a team may happen to play the bottom of the conference twice, while another plays the top twice. That is why the concept of "bad losses" and "quality wins" have been introduced.
Whether it has happened or not (have you REALLY checked EVERY single case since the first T?), a major conference team with 12 league wins (and an inflated OOC w/l record thanks to "cup cakes"), MAY AND SHOULD be left out of the T if the vast majority of its wins came against very weak teams at the bottom of its league, and the rest over mediocre teams.
As I have said multiple time, without the Wiscy win, the cats have ZERO win against a major-conf team that is doing well (clearly above .500) in its league. After Wiscy, they have ONE win that satisfies that definition. Still too few, in my book.
With my proposal, the cats would have at least two legit quality wins (WI + PU or Mary), plus avoid a horrible loss (Rutgers), while limiting to one additional bad-to-"baddish" loss (Indy/Illy/Mich). That is a recipe to ENSURE an AL-bid.
Not just having 12 league wins, as if all were worth the same.