Not sure what things are like post-COVID, but back when I was commuting weekly, my hypothesis was that the last arrival of the day tended to go to T2B, and consequently, the 6.40am departure would often be from T2B too. In other words, they would use B if the aircraft had to overnight. I don’t recall ever having had a B departure/arrival in the middle of the day, but I always made it a point to ask for the gate number when entering the lounge (and they would always say “we can’t guarantee it, but it looks like A2x”, which it would invariably end up being).

Unless you need the exercise or know the flight is going to depart from there, I wouldn’t go all the way over to the B concourse…