The short answer is no, you’re not protected by Cathay so if they scam you there is nothing you can do.

People do sell gold nominations tho, so there is at least a chance that it is legit. It’s a YMMV situation. Whether you trust the seller or not.

On the contrary, although those cooperate contract diamonds nomination do exist, CX does check who you nominate. And you need to give them really quite a bit of revenue to be given diamond nominations. So I doubt they are selling these, and even if they are it probably won’t be for just 20k rmb.

I don’t have concrete proof they are 100%scam, as I don’t dare to try. But it’s very likely given how some of them also claim to sell LIFETIME platinum pro or Concierge Key etc…