You’ve probably noticed this already, but I’ve found that when I select to display only public notebooks, after I page past all my public shared notebooks I get also returns for my private - and then shared - notebooks (rather than the list just ending).
https://beta.observablehq.com/@aaronkyle?types=public (for me the private notebooks start on p2. As mike has 486 public notebooks, it might take a while for him to page that far backward to start hitting private ones 
)