I often had to chase these in the past and Barclaycard always blamed BA. They told me that BA tracks your progress and issues the voucher when the threshold was reached. This would be supported by the fact that I always got an email from BA and not Barclaycard when that happened. More recently, I got one voucher randomly when I wasn't due one and had to chase others, so it seems to have gone out of sync.

Still a well done to that BA agent for being proactive though.

PS. In my case, Amex will be the winners after the BA and Barclaycard termination.