I don't see why the observation of thought processes is anything special or different from making mental note of anything else. For example, writing out one's thoughts and playing with the words - does that require a special aspect of the canon for some reason?
What I'm trying to describe is more than just a mental process. It seems to me that it is a direct source of knowledge about an aspect of reality - just not external reality.
I think that as Joshua observed repeatedly during the podcast,what we are really talking about here is contact with the outside world.
I think you're probably right that Epicurus intended the canon to be strictly about knowledge of the external world. Unfortunately then it's not a complete epistemology (in my view). It would be sufficient for physics. When it comes to ethics, I think more could have been said.
I am thinking that this entire discussion is not devoted to introspection, but how we make judgments about things in the outside world. Introspection is certainly an important subject but I don't gather it is really what is in issue here in combating skepticism.
The form of introspective knowledge I'm thinking about actually is important in making judgments about the outside world - specifically about the behavior of other people and the best ways of interacting with them. It's the basis for empathy.