I'd just like to add that for me, it made perfect sense. Not only is he a river god who has seen people in all their different states of humanity, he's also spending time around Luke and realizing hidden strength he once wrote off. A river is ever flowing, but Kota has chosen to take root for the time being and is changing from that. I think this is reflective of how he is interpreting rebellion. It's a little awkward, but there's a lot of experience, second only to Asterion.
I think having Kota of all people give permission to you to not necessarily pursue things, but to feel these things, is an important part of the power balance. You are going through something similar to Asterion by not allowing yourself to want. Of course, yours is discipline, whereas Asterion's is embedded, but that's why Kota acts as a sort of link connecting the two to their natural conclusion. I don't think any other character would have that effect, although Luke likely softened you up to hear something that's simultaneously more gentle and more powerful.
(Actually, Luke's comment about Mom and Pop shops is slightly damning. Because it showed you were still considering Asterion as beneath you and something to be handled instead of given full agency. But it's understandable why you're not ready yet. It's a perfectly reasonable response to all that power.)