clearstream
(He, Him)
I think you were mistaken on that last one -- the part about GMs can never be limited.Pretty much, yeah.
Otherwise, soon enough it's bohemian catgirl ninjas all the way down.
When it comes to following the rules, some GMs hold themselves to be outside them (either wholly, or in given respects) while others hold the rules to apply to them (they're not free to disregard or break them.) Either can participate in a sandbox mode of play (the quality is orthogonal to the mode of play.)
But when it comes to upholding what has been established, I believe that is a limitation that GMs commonly impose on themselves as part of their participation in a sandbox mode of play. (Call that (iv), continuing my qualities numbering above.)
(@EzekielRaiden as possibly of interest.)