Was the 2015 Nebraska victory ultimately much different than the 2021 Wazzu victory? Or 2012 GaTech or 2016 Miss St or even 2014 Virginia?

They were all 5-7 or 6-7 or 7-7 or 7-6 P5 teams with Sagarin ranks in the 40s. I get wanting to give Nebraska extra credit because they're Nebraska... but beating them was about the same quality as beating Washington St

On Tennessee I kind of agree, but I gave deference to victories over ranked teams (or teams that finished the season ranked).  If you're just going by Sagarin they could push up 3 to 5 spots, but I tended to prioritize AP Polls (where available) over Sagarin ranks.