No - you are right
everyone can purchase there own - there ID (room key) will say
DVC member - and that is all the front desk needs to give them the 10% discount.
I think they are crazy (okay my opinion) - I think the UPH is a bad deal - I am in the minority.
if your guests are not staying in the same villa that you are - remember the reservations must be in their name or the front desk will not let them check in.
here is what the member site says
"Walt Disney World® Theme Parks Admission Discount
Members receive a 10% discount on the Ultimate Park Hopper Ticket. This ticket provides unlimited admission (except for activities/events that are separately priced) to the Magic Kingdom® Park, Epcot®, Disney-MGM Studios, Disney's Animal Kingdom® Theme Park, Disney's Blizzard Beach Water Park, Disney's Typhoon Lagoon Water Park, Downtown Disney® Pleasure Island, DisneyQuest® Indoor Interactive Theme Park, and Disney's Wide World of Sports® Complex (valid only on event days, some events require separate admission). This ticket is valid from the moment you check-in until midnight the day you check-out. Offer available only to Members staying at a Disney Vacation Club Resort."
the last sentence deals with member trying to get the discount when using their points for the WDW resorts.