If it was a quilted gambeson, that would make a lot more sense, but it seems quite clearly to have a shape and structure to it - see in particular the shoulders

If it was a quilted gambeson, that would make a lot more sense, but it seems quite clearly to have a shape and structure to it - see in particular the shoulders and, in some cases, what appear to be breastplates shaped to emphasise the bust. So if it's meant to be cloth, it's apparently cloth over metal plates, which is the opposite of how a gambeson works. And if you look closely, it really does appear that the white armor has a 3D textured surface that is a lot more like scale than it is like quilted fabric. I agree that it doesn't look much like any sort of armour, but I think the show was aiming for scale.