I understand that the Dark Side and Darker Side have a distinction between Duplicate Moons and No Duplicate Moons for the sake of the extra moons that become available in the shop after the credits roll.

My question concerns any% or World Peace. None of the runs I've seen thus far have included a moon purchased from the shop in any kingdom besides Wooded Kingdom. Is there a rule that prohibits purchasing a moon from another kingdom, is it just an unwritten but followed rule, is it just not fun to watch, or has simply no one tried it?