Honestly, I think from a ARR stand point that we as the player character are "The 6th Warrior of Light" With Derplander and his four comrades being out predecessors that vanished and the player character being a newly selected warrior of light with their own path and story.

Derplander and Friends are specifically representatives of Legacy Players which, for the most part, have their existence completely ignored due to collective amnesia. I think the story was written with the non-legacy model of "These guys have never seen 1.0" and ergo that conversation with Ifrit didn't happen WITH THE ARR PC.

There's also the fact that Ifrit has fought and tempered a lot of people since the legacy players met him. (Since I never made it past level 16 he never met me in 1.0 any way)