Check out this, got the email a few days ago that my UG had cleared for MSP to SDF tomorrow. I go to check in on my phone and see I'm still in seat 5D, which is an EC seat. So I try Delta.com and I see the same thing, but it has me as "Medallion Upgrade Confirmed" and shows my fare class as Economy(RU).
Seat map had me in 2D when I got the UG email and that seat is still occupied, hopefully by me.