This feels like a stupid question, but do most agents inquire about roommates and add them as listed drivers? I almost never see another agent's policy that has roomies listed. Is this an area where a lot of agents follow "don't ask don't tell?"
Progressive can and will deny a claim involving permissive use if the household member insured elsewhere was never listed. They will pay a lienholder if involved however discriminatory and unjust that may seem.
An overlooked reason why rates increase is too much loss payout. Carriers not getting appropriate premium for the household risk often because agents don't ask.