Defensive impact goes beyond stats, though. Deflections aren't much better than steals and blocks when evaluating defense, not that it means it isn't good but you have to watch. When I watch Matisse I see him cover more ground, help better so yes, it's eye test. I can't seem to trust defensive stats much when there is so much they don't input. Not that I don't include them in my evaluation, though.
I agree Matisse plays with better defenders and Shaq's on/off numbers indicate he is a good defender.