As I played the game [and replayed it] - one of the things I noticed was how the other fayth treated Tidus. Fayth pretty much ignore everyone except their summoner ... and Tidus. At one point Tidus is thumping on & crying against Pterya's [Isaaru's version of Valefor] chest.

Sure, Tidus might be getting away with this because he is the protagonist - but it could also be professional courtesy. That the fayth recognize Tidus as being one of them. IMO Tidus -is- Yuna's 'fayth of the final summons'. He shows up on Besaid while she is undergoing her trial - and is with her through the pilgrimage.