Hell, nowadays most major corporations do this. Just nobody uses the scare word “propaganda” to describe it.

Correlation vs. causation.

A lot of things which impact “intelligence” can also have varying impacts on speech/articulation/communication skills. However it is important to note that the correlation isn’t strongly positive or negative (IE savant syndrome).

So while some disorders may have some common correlations with specific speech/articulation patterns they (usually) are not good diagnostic criteria and extremely broad generalizations like the one above are particularly bad.