mystery spot is made so much more interesting retroactively by the decision to make the trickster an archangel. it becomes, uniquely, an early seasons instance of heaven’s approach to manipulating sam and dean into the apocalypse.
when the demons try to manipulate sam and dean (mostly sam) in the early seasons they do it largely via normal human methods of manipulation — lying, saying things to put ideas in their heads, gaining their trust and then trying to push them apart, etc.
but when heaven manipulates them, they rely heavily on reality warping scenarios. we see this most obviously in zachariah’s alternate universes (the end, it’s a terrible life), but also when they send dean back in time to see mary make the deal (in the beginning). both of these also take the form of trying to “teach them a lesson”. and even changing the words of dean’s phone call to sam in lucifer rising and the shapeshifting pocket dimension of the beautiful room fall into the reality warping category.
gabriel might not be actively working for heaven in mystery spot, but in trying to convince sam to accept dean’s inevitable death and trip to hell, he’s still working towards their plans for the apocalypse, and he’s certainly using their strategies.
