DS received his USMMA LOA a couple of weeks ago. It is dated 16 Oct, so they have most likely begun the process of reviewing records. This particular LOA states "an appointment has been reserved" which is actually worded a bit differently than the CGA LOA he received in September.
His application was complete in July, and DODMERB was accomplished in early August...so it took a couple of months from that point. I do know that the admissions portal system was undergoing some changes. DS was sent a link along with instructions on how to set up the portal access about a month ago.