the final day is people hearing the song that come across the space. the song don't simply aim at area it's something affecting the whole world. sharlayan wasn't as much affected because it's a place filled with people that are focusing on something and don't fall easily into despair, what is creating the transformation. however, tural is not the same... even if, let's say the capital people are living without failing to despair, people in yak tel can't be said to feel the same. (that an example) without forget that rat a moment the monster was affected heavily by the song, what did lead to the dungeon where you have radz at han attacked, without forget that people did learn and share the information about how the final day affect people throught the alliance.
what one more time wasn't the fact for tural with the limited contact with the exterior world.
another point that contradict this, is emet specifically talking about how we don't know how the final days did affect by example, merycidia. here it's litterally like nothing did happend... in case of invasion from the empire, it was normal that other continent that had almost no contact didn't know about it.... here the final days are a global event. something that was not born in etherys, but from space.
for me it's a plothole, it's not because we say, yes it didn't affect tural because, it didn't affect the whole world the same. if that was something born from the world yes, but for something coming from space it make no sense. period.