I'm not entirely sure how the quadrants in NET are defined, but in the way KenPom defines A-tier and B-tier games, Gonzaga is 5-2 in A-tier games and 4-0 in B-tier games, so it's pretty similar to the NET quadrants.
Iowa State is A: 4-3 and B: 3-2 for comparison.
So Gonzaga is pretty legit, even though their overall schedule is probably littered with lower tier teams (I have no doubt that they're a top tier team, just curious on how it looked on paper).