Interesting. For me they help follow what he's saying: after a few minutes I can peek at the doodles and I remember what points he touched.

I never thought some people might dislike that part, but now I see you and a sibling comment do.

I wonder if it's good for people like me (who don't know much about music theory) and bad for people in the field. If this is the case I believe it's a good choice: the audience of non experts is much bigger and thus the minority of viewers finding this annoying will outweight the problems of those who dislike it.