EA reserves the right to change and update the EA Access Services, and the EA Content offered through the EA Access Services without any liability to you. In particular, Vault Titles are subject to change and may be removed
I'll take a look at the dashboard when I get the chance, as I read something in the EA Access Hub that explicitly stated that Titanfall would not be added. I'll try and take a pic.
Edit: Weird. EA must have updated the TOS, as I swear there was a splash page or TOS that stated explicitly that Titanfall would not be added to the vault. Maybe they made a deal with Respawn and it can be added.