As someone who enjoys doing sidequests as they appear on the map, I found that this one describes what is to happen in the MSQ quest Dawn of a New Tomorrow despite appearing before the quest. I don't mind spoilers, but I still feel like it is made available at an odd time since it isn't hinted before that quest that the events described in said quest will be happening.
I completed this side quest and main story beat yesterday, and I agree.
Currently, the quest "Once A Riddler, Now A Ruler" becomes available in Tuliyollal upon completing the main story quest "Road to the Golden City." Ever since Endwalker, my play-style is to complete all side quests prior to continuing major story beats. After completing "Road to the Golden City" and returning to Tuliyollal, I knew the next main story quest would be an important one, so when I saw a few new side quests in Tuliyollal, I decided to complete them prior to starting "Dawn of a New Tomorrow."
My suggestion: make the side quest "Once A Riddler, Now A Ruler" available AFTER completing main story quest "Dawn of a New Tomorrow" to ensure players see the events of "Dawn of A New Tomorrow."
My reasoning (contains the spoiler): upon completing the three riddles and returning to the quest-giver for "Once A Riddler, Now A Ruler," the quest-giver's dialogue spoils an important moment in "Dawn of A New Tomorrow" by saying something to the effect of,"Now Wuk Lamat and Koana rule together." This spoils the surprise of Wuk Lamat naming Koana as her Head of Reason and the two being Dawnservants together.
I didn't view the spoiler as a major deal. But I believe the fact you CAN spoil an important story beat should be adjusted by simply making the side quest available AFTER completing "Dawn of a New Tomorrow."
It's been confirmed as a bug that they're planning to fix: https://forum.square-enix.com/ffxiv/...ler-side-quest.