Thanks for the replies.

I didn't think to check Y.

Inventory shows how Y5 B5 M5, which makes me wonder if the two upgrades who have cleared actually booked as Y.

What exactly is the seat map in J showing if it doesn't match inventory?

(And out-of-scope, but why does economy's seat map match inventory even less? There are something like 50 open seats on the seat map between Y and Y+ on UA102 tomorrow...)