"Allow to open in a new window" - why not for all perspectives?

Why do some perspectives in OmniFocus have the setting “Allow to open in a new window” while other perspectives don’t have it?

When I choose a certain perspective, I don’t want it to override the one which was present in the first place.

Is there really not a simpler solution than useing an OF script to do this?

Any assistance will be much appreciated,
OmarKN