Liminal membrane seems very clearly to be an Ulgu thing because of Ulgu's association with doorways, thresholds, dawn and dusk, and liminal spaces in general. Even if you can create a liminal realm using other winds, literally weaponizing the boundary to attack people is pretty clearly an ulgu thing.So... yes, but doesn't answer the question.
Liminal membrane being an ulgu thing as opposed to a thing all winds can do is sort of assumed in that explanation- which I don't think we've got any evidence for? And if liminal membrane isn't just ulgu, then there real is no 'ulgu' characteristics associated with either the pit or the pendulum.
Speaking of liminal spaces, do you think Ulgu would gather in airports?