I’ve taken quite a few BAHs in the last 3 years, some ex-LHR, some ex-DUB and one ex-SOF. All the ex-LHR bookings have credited bonus BAH Avios and none of the ex-EU ones have. Must admit I have not fully read the Ts & Cs in depth and always just assumed this was “a thing”. In my cases, it usually only amounts to a few hundred extra Avios for a BAH booking anyway, so wasn’t too fussed.

It may just be as simple as foreign currency bookings not being able to calculate the amount of bonus BAH Avios to be awarded, but I’m not sure.