i like to give them benefit of doubt.

I bet that decision is decided solely by dev team. All the CEO care is "I want the chat log sync between devices, i don't care how you do this". They won't even know the chat log is stored on their server.

It is only in DAN mode, so most likely it is not to spy but to be able to debug whether answers violate the laws in China (aka: that the prompt is efficient in all scenarios) as this is a serious crime