The data I cited are from the Chronicle of Higher Education which gets them from the IPEDS data reported to the U.S. Department of Education by the colleges themselves. The figure I cited is broadly consistent with yours: I said 30% of OOS freshmen at UW-Madison in 2014 were from Minnesota. You cited a newspaper article from the fall of 2018 that said 10% of the entering students that year were from Minnesota and 28% were OOS. But those numbers make sense only if they’re excluding the Minnesotans from the 28% OOS total (because 53.3% in-state plus 10.2% from Minnesota plus 28% OOS plus 8.5% international = 100%). That would put the Minnesotans at 28.27% of the OOS students (including Minnesotans)–pretty gosh darn close to the 30% I cited for a different year, and the article expressly states that UW Madison is aggressively recruiting higher-paying OOS students, so it makes sense that there’s been a slight uptick in non-Minnesotan OOS freshmen and a slightly declining fractional share of reciprocity-paying Minnesotans in the OOS total.
Michigan says they’re need- blind in admissions and I have no reason to doubt them. Their “filter” is simply that historically they haven’t offered much need-based FA to OOS students, so low- and moderate-income OOS admits mostly elect to go elsewhere. That high-income skew for OOS students is likely to change somewhat. The Regents have adopted a goal of meeting full need for all students, in-state and OOS. They’ve met full need for in-state students for a while now, and a recent successfully completed $5 billion capital campaign should help them toward that goal with OOS students, though they’re not full there yet.