The depth and clarity of the advice and the effort put into presenting it work as solid credentials in this case. The author is clearly a “doctor” of design.
Look how well those those graphics get their message across, whilst also matching the style of the text. That takes a real steady hand (both literately and figuratively).
Replace a doctor with a random stranger (which is what this website is, I don't know the person giving advice about the modals) on the street who is obese and tries to tell you with authoritative voice - "Hey! Listen, you're fat and this is how to lose weight!".
That's more accurate. I can agree with you about the entertainment value, I personally don't see it but if someone is entertained by it, good.