Just my gut feel, but I believe the Michigan admissions system is sophisticated enough to be able to detect an 11/1 deferred/postponed vs. a 2/1 app RD submission. Michigan has been using those deadlines for a very long time.
As to why they’re sending out a LOCI to 2/1 submissions, I’m not sure, other than maybe most of their RD app submissions arrive in the November to mid-January time frame and they’re wondering if the applicant remains interested.