The "replace text with visuals" example, whilst funny, actually suggests that the reverse is true in some cases. The question, as always, is "What information are you trying to get across?" If you want people to understand that a circle is a shape of Euclidean Geometry, whatever that means, then only showing them a picture of a circle is clearly insufficient!
Same with the bullet points example. The final bullet tells me so much less than its paragraph equivalent. The richness of the information is diminished to the point where the final bullet is almost meaningless.
I'd challenge the convention of even referring to e-learning pages as "slides", as it encourages us to employ *presentation* design principles to things which are not always, and indeed often shouldn't be, in any way related to presentations. By all means, cut back on your paragraphs if you have an alternative means of getting your message across, but over-simplify your content, as this article does, at your peril!