I have not heard of this Jian Shui clay either and am a little suspicious about a claim that says moisture resistant in an unglazed pottery. Yixing teapots are not moisture resistant. In sourcing from China, it is better to be suspicious and investigative first.
As for Chaozhou pots, I am not sure they are preferred for Phoenix oolongs for its thinness or whether because both the pot and the tea are from the same vicinity; Chaozhou people has a very strong local culture and self-identity. They are a proud people.
As for whether a thinner pot is better for preparing these dancong teas, it is because people there always use water almost at boiling point. If the vessel holds heat too well and if they infuse their tea for longer than 10 seconds, the tea inevitably becomes cooked and the taste adversely altered. That is why most Chaozhou people never really understand the true taste profile of their own tea. Actually, before I began to advocate it, people were still saying 100°C for infusing the tea (and most other oolongs, for that matter).
