> Saying "we don't know for sure" is dissembling nonsense that can be stated of any claim. It's a transparent device for sowing disinformation without challenge.

It is that at times. At other times, it is simply something people say when they suspect something but do not know it for sure.

Agreed. I suppose you have to simply consider the context to help determine which it is. If it follows a load of other dissembling nonsense, then it's probably the former.