Cover usually follows the car
If you lend your vehicle to a friend for an afternoon, your policy generally responds to a crash, and your limits and your claims record absorb it rather than theirs. That is permissive use, it is genuinely useful, and it is also why lending a car is a larger favor than it feels like.
Regular use by a resident is not permissive use
Someone who lives at the address and drives the car routinely is a household driver and belongs on the policy, whatever the arrangement is called. This is the single most common reason a claim is questioned, and in shared housing it happens without anyone intending it.
An excluded driver is excluded completely
A named driver exclusion is a legitimate tool and a blunt one. If that person drives and has an accident, there is generally no cover at all, not reduced cover. It solves a specific problem and creates a serious one if anybody forgets.