This is a deep discussion. Really beyond a chat board exchange. A matter of statistics, where prediction and evaluation can be debated even with complete data.
But, that's the operative term: complete data. What is that? A full season.
Each game obviously must be reevaluated as the season unfolds. ND losing to NIU weighed heavily at the time. Less so in lieu of how things have gone till now.
Sure, some teams might have been ranked higher than they should have. Some teams that weren't ranked now are. Some teams are yet better or worse than their rankings indicate.
I will say this: over and over complete season, results and weightings should normalize to their approximate truth. Again, statistical analysis may not be fully predictive, with some margin of error. We all know this by common sense...especially that you also have to apply some human judgment, that so called eye test.
My take: ND generously is ranked #6 in some polls. I don't mind. In my view, the aim of these nebulous polls really is to ensure the best 1st 6 get into the playoffs...tolerating some error with the last 6. ND deserves to be in the playoffs at this time. Win out with conviction and 100% ND should be in.
Fair overall.