Perhaps if you had been talking about difference rather than causation, your point would have been better made.
Unclear articles often omit details. But lack of details can not be a *cause* of unclarity, any more than a lack of decorations can be a cause for a lack of cake. The cake may have less decorations, but still have lots of cake.
I disagree, if you miss out a key piece of information it can make what remains unclear. For example, an article on a mathematical concept that doesn't include a definition will likely be very unclear. I would argue that such omissions are the primary cause of a lack of clarity.
An article may omit any amount of facts and still be quite clear on the heart of the matter
Indeed, as I said, the converse isn't true. Lack of clarity implies lack of information (in many cases at least, sometimes the information is there, just badly presented), lack of information does not imply lack of clarity.