Closed eye visuals/hallucinations is pretty vague because certain levels of closed eye visuals/hallucinations can be seen by completely sober people without even trying and most people would not consider them a hallucination in the common usage of the word. Ive certainly never heard of from others or experienced any unusual closed eye visuals from cannabis outside of seeing it as a tv trope or government anti-drug ad. I could see it being more noticeable or slightly more active than normal while on cannabis certainly but it still seems inaccurate or perhaps deceptive to tell somebody that if they smoke weed they might have hallucinations, at least not without a much more thorough explanation on what kind of hallucination they are talking about.

I know it can also cause psychosis, but it's still rare.