Yes for generic 9th grade English or poorly taught science classes it is easy to just use ChatGPT. His class would've been pretty immune to GPT plagiarized assignments though, assuming a serious grader were evaluating them, which one used to at least. Yes GPT could've been used to assist in the writing itself, but that wouldn't disrupt the educational goals achieved by developing the content, which required synthesizing multiple modern scientific papers in a coherent way.
In any event, he isn't concerned at all about students using it for assignments, it's the degree to which he seems to think it can be integrated in his current curriculum that alarms me. I think he is misunderstanding the capabilities and therefore pitching something that doesn't actually make sense.
The other teacher I didn't follow as closely, I just got a kick out of seeing she was now advertising some sort of webinar about ChatGPT filled with buzzwords too.
Also if a teacher is really serious about wanting to plan around what GPT can and can't do to the point they want to be a teaching authority on it, they should be consulting with people in the relevant domain. When I want to use a new tool in the lab I talk with colleagues that have a great deal of relevant experience before I start working it into experiments. I can't imagine starting to give advice to others on the matter when I don't actually know the current nuances.