The Start menu pin list is just a list of items; there’s no magic
Commenter Kevin Dente asks, “Is it possible to put a folder on the Start Menu Pin list and have it cascade?”
No. The last time I checked (which was back in Windows XP), the Start menu pin list was a list, not a menu. (Specifically, a list view in tile mode.) When you click on the icon, it launches. There is no code to say “Oh, if this flag is set, then let me draw a little menu arrow next to the item, and if the user clicks the arrow, bind to the target of this shortcut, enumerate its contents, and create a menu from it.”
Remember, features don’t exist by default; somebody has to implement them.