Really, this seems like more of a semantic debate around "changing reality". From my perspective (and presumably
@Aldarc's from the example posted), reality never changed, because it was never explicitly stated that there wasn't a path there before. The player simply negotiated, based on character concept, what the actual fictional state of the palace is.
Now, to a dedicated simulationist, this feels like a "change", because simulationist play runs on the assumption, the
feel, that the fictional setting is already cast and the characters (and the players through them) are discovering that fiction through play. Whereas, to players used to a narrative style, you simply assume that all the details of the fictional setting are fungible until declared in play; no setting details are being changed, only "created" to fit the narrative.