This sounds like a great resource, am I missing something or are there only two chapters and one is dedicated to piano tuning? Or is this more of a meta resource that tells you where to go to learn something like chord theory etc?

Yeah, I don't know why he organizes like that. If you click on chapter one, you'll find basically an entire book of information in that one chapter.

This resource doesn't actually teach piano per se - it teaches "piano practice". In principle, you could use this to learn whatever you want.

Thank you!