Having spent an hour on the phone with BA I just don’t think what you say is true. Even if they had been back to back they were two separate tickets and it makes no difference. They could not have been more helpful on the phone but they were very clear that the fare rules meant the ticket had to originate in Amsterdam and if I did not present there to take the flight, regardless of the reason, the ticket would automatically cancel. I don’t work for BA I am simply reporting for others benefit what I found out. Based on that I do not believe it would have made any difference if I had flown the same day. It would have had to be a different ticket.