Wow, you're kind of amazing. It's not easier for a 9 to beat an 8 compared to a 1/16, but it's much harder to string together wins in a single elimination tournament. So if you are a 1 seed you have to win 4 games in a row and every time you win, you play a team that has done the same thing. Usually a hot team.
In the last 6 years KU has actually exceeded their seed by 2 games two different times. That's a lot harder than it sounds. ISU has never exceeded their seed by 2 games. Plus KU has reached or exceeded their seed 50% of the time over the last 6 years. During that same time, UNI is the only team KU lost to that didn't end up in the Championship game. Please give me one example of a team that has several high seeds that hasn't underachieved. The closest I could think would have to be Duke because his Elite 8 record is crazy good, but even Duke has underachieved the last 3 years in a row, including losing first round as a 2 seed.
After saying all this, I will bet that KU will not reach their seed this year because of their point guard play.