I rewatched the cutscene and now I'm not sure how close or distant Turali is from Eorzean based on what Wuk said but the language change was "some time ago" which I took as being when Tuliyollal became a nation 80 years ago:
We know Ketenramm, a Lominsan, was bouncing around the continent right at the same time Gulool Ja Ja unified the region under Tuliyollal so he's probably the genesis point of the language. Wuk Lamal also has no problem communicating with us, same with all of the Mamool Ja we've ran into at this point. I think it's still a toss-up as to whether the 1 word we see is an Eorzean loanword on a sign in a fully Turali town or if Eorzeans are directly involved there. I got the feeling that the whole ceruleum fiasco with the Whalaqee was a one-time thing since everyone was hyper-focused on their land specifically instead of anywhere else with ceruleum, but I wouldn't put it passed the writers to take old lore and milk it more than it needs to be.Wuk Lamat: Given how culturally diverse Tuliyollal is, it was decided some time ago that a common language was needed.
Wuk Lamat: But instead of elevating an existing tongue, and its speakers, above all others, we looked to those widely spoken overseas and created an altogether new one.
Wuk Lamat: These similarities to your common tongue also make it quite easy to communicate in these situations, no?
Wuk Lamat: This letter, however, is entirely in Eorzean. If Father had written this, it would have been in Turali.
This also brings me back to the multiple background Miqo'te in the Dawntrail trailer. Their clothes look Eorzean, but we know Wuk Lamat has a Miqo'te brother so they could be Eorzean-influenced people from Xak Tural since that goes with the whole Arizona vibe.