Opinions

I think one of the major reasons is because there is a power dynamic between them. I would also like to hear everyone else’s opinion.

Yes, I think so too. I think because of the power imbalance, Lau feels that the bond between him and Xin isn't "real" per se? As in, since they've been forced together there was no room for their feelings to naturally grow and develop. They've been resolved to this predetermined destiny to belong together, which only drives them further apart, despite not being able to live without one another.

the power imbalance is obviously a huge part abt it, but i also feel like lau's too emotionally constipated and traumatized to even admit he loves xin. we know lau has abandonment issues from his sister, and knowing that xin could just leave him at any time, ig lau never wanted to show xin that vulnerable side of himself. the fact that xin actually left him before doesn't help at all. idk how they're even going to repair their relationship after this, my boy lau's basically been shellshocked and i think it'll be very hard for him to trust xin after this.

as for xin i think he feels that (in the present moment) it would be a burden to lau or maybe that lau would just see it as another way to control him. xin was pretty flirty in the past tho haha in the aquarium flashback he's already saying he loves that fish (the fish thats supposed to be like lau lmao).