Also on the whole “the king his book” thing, I think the video kind of agrees with you but in an awkward sort of way. He points out that the belief that it’s an abbreviation for “his” was incorrect, but where it gets confusing is that it’s implied that that incorrect belief is why the apostrophe is used as a possessive, rather than as a marker for the elision of the “e” in “es”. The overall impression is that grammatically it would be correct to just leave the apostrophe off and just add s to show possession. The reason I think he brought up the debunked “his” theory was to highlight where that leads to incorrect over correction by some writers where they replace the possessive with an expanded incorrect “his” version.