There are Y fares that are considered "full fares" that sometimes don't qualify as a Y-up. Y-26 fare basis is really the only "full fare" coach ticket.

However, that said, I've never had this happen where I bought a Y that wasn't a Y-up and didn't get me up front right away. Yet, there are posts once every few months from FT'ers who are angry that their "Y fare" didn't get upgraded, only to find out that not all Y tickets are "full fare". Confusing... I know.

If you are concerend, book the ticket and call the elite line. You have 24 hours to cancel the ticket free of charge.