ActorPosition or ObjectPosition in a decal material

When using ObjectPositionWS in a decal material then an “undeclared identifier” error shows up. According to the docs that node should output the world-space center position of the object’s bounds which is meaningful in case of a decal.

ActorPositionWS compiles but I couldn’t make sense of it’s behavior: it flashes colors which seem to be dependent of camera orientation and not actor position.

Are these bugs or expected for some reason?

4.7.3 binary, windows 7 64bit