Hi,
No, I don't use this feature on the demo as it's not needed for that demo, because there is only one scene for the room.
You can have different players in different rooms but that's going to be on each instances, Unity can not be in two different scene at one time. Your example of a building made up of several scenes is totally ok to do in Photon, your players can be all in the same Photon Room on the server and be in different part of your scenes, or even have different scenes loaded asynchronously or completyl switched to other scenes, it doesn't matter for Photon, as long as networkids are respected ( which they are by default).
so in your case, you don't want this to be set to true, and o leave it has is I would say.
If you need, I can build the custom action to let you setup this option. But indeed, this is not what you want for your case.
I think that in your case you are doing something wrong, like maybe actually joining a totally different room, that's likely the problem.
Are you loaded a new scene completly or adding it additively?
Bye,
Jean