Join in progress clients won't receive that a net startup actor is hidden

This seems to be because IsNetRelevantFor checks if the actor is hidden, resulting in a hidden actor not being considered relevant to clients. However, if it is a net startup actor, this will result in the actor being visible on any client that joins after the actor was hidden.
This is further complicated if placed-in-map instance of the actor has a different value for "Actor Hidden In Game" than its default object (see linked UDN and [Link Removed] for more info).

On the server, set a net startup actor to be hidden in the game (bHidden = true).
Have a client join this server after this actor has been hidden.
Expected: the actor will be hidden on the client.
Actual: the actor will be visible on the client.