Anecdotal recent evidence from a UK Presidents Club member.
Original assigned car (Kia Sportage) was the category I booked (intermediate SUV).
When I went in and without asking to see the card (I said I was Presidents Club) I was offered a Ford Explorer Sport (which I think is about two or three categories higher).
My receipt showed "Preferred" as status level.
In terms of booking, the Avis UK website was much cheaper than Avis US website.