Absolutely right - the terms and conditions are very clear on this, and I enclose an extract below:
2. Subject to these terms and conditions, the Member is entitled, with up to eight additional travel companions on the same booking and paying at the same time, to a discount of 10 per cent on any BA published fare for leisure travel only (the ‘Shareholder Discount’). This discount applies to flight only and cannot be used when combined with a package (e.g. hotel, car hire, excursion or car parking). The Member and any travelling companions on the booking must travel together on all flights throughout the journey and have the same booking reference i.e. booked on the same booking.

If you were talking about getting something for nothing I'd refer you to the current thread Down with these saddo upgrade hustlers