Clojurians Log v2

say you have a map { ... K V} and you are transforming the map via ALL with a transform function which returns NONE for V, strictly speaking you return [K NONE]. This seems to remove the [K V] pair entirely (exactly what I would like) but I can't find anything in the documentation indicating that this is the intended behavior. There are things addressing map KEYS being xformed to NONE for removal, but nothing about values. Is this intended behavior that can be counted on in future?