I don't know.
UW's losses are to Providence, @OSU, MSU and @IL.
All are ranked teams in both polls. Providence #11 in AP. OSU 16, MSU 17, IL 13.
NET #25, #18, #27 and #12, respectively.
Then you look at win quality. I don't get it.
This is a good point, and the reason that it doesn't track with win quality is because it's a tool that's not designed to measure that primarily. If anything, it's mostly there to track the quality of each win for assessing a resume, i.e. it's to give us that second batch of numbers.
These rankings ar basically designed to pop out a score that roughly equates to strength and how hard a team will be to play. In basketball, the main metric at its base is blending scoring and schedule. Winning big and losing close is better than losing big and winning close. Doing those things better against a better schedule is better, obviously.
I think this UW-Iowa quirk is more about UW than Iowa. Iowa is maybe a bit above where you'd expect their record to be because they've been relatively competitive in losses and dominant in wins against a pretty good schedule. UW has faced a better schedule, but is more often playing like a team worse than it's record (not being in it late in three of those losses, getting pushed by PSU at home, Minnesota at home, a Southland conference team). So that's dragging UW down. It's also worth noting that with any ranking of teams, there will be some oddities, and this just happens to be one on front street.
It's important to note these are less "rankings" in the sense that it's saying UW is definitively behind Iowa and more just stacking numbers. So they might be 0.1 points apart, which is functionally nothing. And ideally it doesn't matter because there's only really a few situations where a team's own NET should impact its tournament placement, and UW is far from those.
(There often is a complaint about this that some teams are just better at winning close games, but for the most part, barring the rare exception, previous close game success is not a predictor of future close game success)