Ah right. There are actually two places the bus can take people. Your door area into the building was, I believe, quite small and the stairs effectively took you up to the end of gate 55 (the domestic area). So anyone wanting to go landside would have had a bit of a hike up and down to get to baggage reclaim, but it put you in same place as an airbridge arrival and therefore able to access Flight Connections. The main bus drop area is much closer to the baggage hall and therefore more convenient for most passengers who want to go landside but you're well past the Flight Connections route. That's a larger area, two buses can work that simultaneously, whereas your door would have been no more than one bus at a time.

It would be nice to think that GAL looks at whether there are connecting passengers on the arriving BA flights (U2 wouldn't be an issue here) and decided which door to use.