NU's treatment from Big 10 refs is a statistical outlier / anomaly. This happens year, after year, after year.
A few years ago I did a deep dive and showed that the differential in Free Throws that NU experiences - non-conference versus in conference - is unlike any other team in the Big 10. NU's differential in this category is routinely the worst, and by a wide margin.
You can also look at the way other Big 10 teams get treatment by Big 10 refs - comparing against NU versus other Big 10 teams. Tonight for example: Penn State, looking at its 3 previous Big 10 games, PSU shot fewer FTs than their Big 10 opponents. And 2 of 3 of those games were Penn State home games. And yet tonight, playing AT NU, Penn State shoots 20 FTs to NU's 9. Even taking away the last 4 or so in the final minute when NU was fouling, it's a percentage discrepancy that they likely won't see again in the Big 10. But teams routinely have their "best ref'd" games against NU.
Look at NU versus Maryland: Maryland shot 22 FTs, to NU's 9. In Maryland's other Big 10 game... they shot 2 fewer than Iowa.
If only NU could get the ACC refs we had for the Big 10 / ACC challenge... playing at Wake, NU shot 18 FTs, and Wake shot 18 FTs.
Obviously FTs are just the most objective measure. But anyone that watched that second half... Penn State had a half a dozen questionable calls their way, and yet Boo Buie goes hard to the hoop and gets grabbed and spun around on a critical possession... refs swallow whistle. He was visibly very frustrated, I guess every year it takes a few games to get accustomed to Big 10 refs giving you nothing. But without fail it happens year... after year... after year.