I’m pretty sure that Devil Fruits comes from people’s wishes is just a theory from Vegapunk. If it isn’t, then…that’s kind of disappointing. How does that even work? Does one just close their eyes and say “I wish for the power of an island” or “I wish for the power to turn into a flying winged Dragon” and poof, the Devil Fruit appears? It’s strange.

Seiryu is a deity so it could've been either someone wishing to protect their people or someone wishing to have power.

I think it‘s more like a subtle desire that a lot of people have, for example a lot of people might think something like: „I wish my body was as strong as this guys‘“ and thus appears the jacket-fruit.