I'm trying to book a SEA-BKK on .bomb, using the setting for systemwide ug reg 2. The results I get only show certain segments that have the tag "upgrades may be available." When I click to buy these flights however, it shows the entire journey in W Class or M Class.

Am I missing something here? My understanding was that both W and M fares were upgradeable using the systemwide. So if I'm right and go ahead and purchase the ticket, can I then request an upgrade for the entire segment using the u/g or no?