If the guest was traveling in Polaris they would have access regardless of the GS traveler. I read this as if the GS is in Polaris and the guest is in economy, the guest is denied.
Similar to the UC access, which IMO is ridiculous. What good is Polaris or UC access when traveling with a guest if the guest can't access either lounge?

In the case above (GS in Polaris and companion in economy or premium economy) the GS would be forced to go to the UC (or none at all) if wanting to remain with their companion!