Expansion joints between a pool's concrete deck and its coping should be a self leveling latex caulk.

Scott

I'd contact the Reflex Rubber people and see if they think it's suitable. Make sure you let them know it's for the the joint between the coping and the concrete deck, not just for the deck itself.

For control joints to break up the expanse of a large slab pour, it's fine.

But as the others wrote, for a pool deck-to-coping joint, A self-leveling caulk is the better option. I use Vulkem 45, a self-leveling polyurethane sealant.