Quick Answer If you just want the short version: There is no company-wide restock day
They do not use the stack, there is no pause between those, players do not gain priority until both are performed
The cards arent covered by the comprehensive rules and are not for tournament play, notably different from being not tournament-legal. While it's true that silver-bordered cards arent legal in any Standard, Vintage, or Modern decks, Wizards still intended them to be used in casual black-bordered formats rather than exclusively with each other
The Beast, Deathless Prince has a casting trigger, which conflicts with commander tax
It is simple to set up and the postage of cards is cheap
That gives collectors enough reason to be completely obsessed with it