Forgive me, but this seems like a very curious distinction.
Doing something statically anomalous in sports is by its nature accomplishing something difficult. You went and did it. A thing that is difficult to do was accomplished.
Now the answer might be that accomplishment doesn’t warrant fringe inclusion in the field, but this feels like it doesn’t make much sense. Michigan being 19-1 in the conference is an anomaly. The way they lost that one was also an anomaly. But both are accomplishments.
That's a good point, but again it doesn't always mean that something rare is necessarily "hard", just that it's statistically unlikely.
As I mentioned, if you have a 97% win probability in 31 games, you have LESS than a 50% chance (38%) to go undefeated. But if that team plays three separate seasons all with the same probability, the expected number of undefeated seasons is three times 38%, or 1.14 undefeated seasons. Do it 10 times, and you're expecting between 3 and 4 undefeated seasons.
Individual game odds are going to be much lower than 97%, even if you're a fairly decent MAC school playing the Little Sisters of the Poor, but that doesn't mean that going undefeated is "hard" more than it's statistically unlikely.
Think of it this way. Flipping a coin 10 times in a row and it ending up heads 10 times in a row... That should happen roughly 0.1% of the time, or 1 out of 1000 attempts. But if you fill a large college football stadium with 100,000 fans and you have them each try it, you'd expect to get 100 of them to do it.
Does that mean flipping a coin 10 times in a row and getting heads all 10 times is "hard"? No. Flipping a coin is easy. It takes nearly no skill whatsoever. But we think getting 10 in a row is remarkable because it's rare.
And BTW... I think everyone is getting hung up on this "in the regular season" stuff. Why should we not include a conference tournament? The NCAAT selection committee doesn't release their brackets until all conferences have completed their conference tournaments. So they clearly think teams should be judged on performance after the "regular season" has concluded. And once you include that, Miami is no longer undefeated.