I have had a flight to BOS depart from an A bus gate - the upside was the gate was right below the CCR, so I got to enjoy extra time there. The downside was that ‘priority’ boarding really just meant extra time on the bus, with of course a lot of standing in a queue up the stairs to the aircraft at the other end anyway: not the best ground experience for an F ticket

this was for the 8pm BOS flight on a Sunday night, so clearly a more peak time business travel slot (for those Monday morning US meetings) and not a time you’d expect LHR to be all that busy at the stands!