I only listed what Michigan considers as its peers. You certainly can disagree with their list. The only one that seems strange to me is UCSF, but maybe that’s only related to graduate school.
UCSD and UCSB aren’t considered the state flagships like Cal and UCLA. ND is a Catholic institution, but that’s a guess. Duke? 
Edit: I see @Eeyore123 answered your question after my post.