The post I quoted said that the GA had also announced, in contrast to the information in an earlier post, that FC had boarded full. I've (rarely) heard such announcements but, more importantly, one should be able to ask a GA this and receive an accurate and true answer.

I think the logic for your name falling off the upgrade and standby lists when you board is that if you've boarded, you're no longer in the gate area to look at the monitor. Information on the monitor next to your name isn't needed by anyone else, so to get all the names on a single screen and make it easier for remaining passengers in the gate area (who haven't boarded yet) to find their own names, the list is shortened when this is possible.

GAs can still see the original ordered upgrade list.