I also noticed that the blog author mentions behavior > introspection and I gave it some thought. Random comments so far:
* I agree that behavior prediction and the inner landscape are two different things (though they will overlap).
* The research referred to posits that our limited self-knowledge arises from the brain's emphasis on efficiency, and introspection is not exactly about efficiency. I'd like to know more about this research before drawing any conclusions on that front.
* Many systems/theories of personality type do ask test takers or self-assessors to report on both their behavior and their inner lives, and descriptions of personalities mix the two, melding them together in seemingly unexamined ways.
* Self-knowledge could be built via a combination of introspection and external feedback, step by step.
/random thoughts