He’s off a bit there. They stopped the show with the end of Book 6, right before the time jump for Book 7. So they didn’t make the final 3 books into the show. There’s hints and foreshadowing for them.

Also the books don’t directly correlate with seasons until Season 4.

• Book 1: Season 1 and first half of Season 2
• Book 2: Second half of Season 2 and first half of Season 3
• Book 3: Shortened and only the second half of Season 3.
• Book 4: Season 4
• Book 5: Season 5
• Book 6: Season 6 (but only 6 long episodes)

People also have survivorship bias with these things. Sure your refrigerator might have lasted forever but quite a few others did not. There is a reason why appliance repair places existed and were much more common than today.

I think that is just HR.