How do the Kitsune react to you being a kitsune from Keros? They don't really treat you that much different than before. Also, don't give others story breaking powers because you can just ask why they haven't solved any conflicts that are happening right now. We can use my WOTR example, when you choose a path you get unique powers that is on the realm of godly but they are only for story purposes or cool buffs, like Aeon being the giga chad and making people cease to exist, or Tricksters being able to manipulate their dice rolls to crit like fucking monsters.It IS said why the PC's soul is special. But if you don't read in a text game, you can't blame the writers.
Becoming a soulbound to a god gives powers and skills, and changes how certain NPCs react to you, but it doesn't give you story breaker powers. What would be the point of having battles, then?
And Keros the Trickster God tells you they'd seen that trick before, and won't fall for it. So if you soulbound to one, you can't barter your already taken soul to other.
You only get a transformation for giving up your soul, doesn't seem that worth it now does it? Lumia makes you a Valkyrie if I am not mistaken. These are some shit offers compared to any other games where you get something like Ebony blade, or Dawnbreaker. I feel that they seen the trick before is such a bullshit excuse because they would automatically know if you didn't have a soul because it is physically ripped from your body, unlike it going somewhere post death. For people who wants to do worldbuilding, it sure is easy to find major flaws in logic thinking about it more than a few seconds.