No, I think they are expressing the idea that people who are fluent enough with the language to prefer written over in-person communication might not fully appreciate the extremely poor reading comprehension of the general population.

I say this as somebody who used to prefer written communication. But I have come to realize that it is necessary to ask your audience, "Does that make sense?" after every major and minor point, and then listen to them reformulate what you just told them to make sure they actually got it.