I tend to trust Mozilla (more than other browser-owning companies), but they really should just clarify exactly what they do that would be considered as sale of data in any jurisdictions.

They seem to be implying that the data is just metadata that has been abstracted for (presumably ad-targeting) commercial purposes, and there are jurisdictions that consider derived metadata as still being “user data”, but in that case just make a blog post laying out what and where you are sharing. If your “partners” are opposed to people knowing about them, or you are scared that people would not like who you’re in bed with, that is a problem.