Why do we give lectures? Why does anyone attend them?
He has a point. In college (both grad and undergrad) I personally got very little out of lectures because Electrical Engineering was very very hard and to Learn Anything one really had to work on it directly. I suppose a tiny bit sunk in during lectures, but often it was simply copying the scribblings of mad scientists (the professors) for future reference. In other words, most learning was when I later read the textbook (and lecture notes) at my own speed and worked on problems and example problems. Some people liked to do this with other people, and I did this a little too, but for me personally I worked best on my own. (At least initially when working on something new. Only when I was getting good at something new would it be useful to talk things thru with fellow students or professors.)
But lectures? Yeah, not so hot.
I could imagine that in some other disciplines it could work if a “lecture” was really a socratic dialogue (as sometimes used in law schools or “classroom response systems” (clickers used in large lectures for aggregate feedback on questions to promote dialogue).
And I should say, I certainly gain value from youtube videos I watch of my choosing which are essentially lectures. Or sometimes new programs discussing topics. But these are within the context of a very high-level, surfacey depth of exploration of whatever subject it is. So maybe that’s a difference. It can spark me to look deeper, but this deeper look is never with a lecture.