Yes, I've noticed this change. My last CO-booked, UA-operated itin, I had the NF and upgrade pending thing, and seatmap would only show F, even though I was only confirmed in Y, so couldn't change seats. Now, this type of reservation, at least in my case, doesn't show the seatmap on UA.com at all - I have to go to CO.com to do anything with seats - that option was never available before.