There is first intent, followed by what people try to get away with.

If BA's intent in providing this service is for people with tight connections hence unable to go to a lounge pre-flight, then they should provide Starbucks with a boarding pass scanner that 'beeps' if the person has been to a lounge before, thus preventing double dip...

At the end of the day, people who abuse the system is costing BA money, and in turn either results in this benefit to be enhanced away, or higher ticket prices for all.