No offence intended to the OP and I hope the blunt tone of my initial question doesn't imply this, but...who cares?

BA Miles and Asia Miles are different programs designed for different markets and therefore targeted at different consumers with different "price" points (as it were) to incentivise them. To me, this is the same principle as a Club World flight AMS-LHR-JFK-LHR-AMS costing 1/3 of the price and offering more flexibility than LHR-JFK-LHR. It's just the way the world works! If you can't exploit it, why worry about it (taking the same example, I can't register for Asia Miles, but I can exploit ex-EU fares...I don't know of the OP's situation of course)?

Phil