How do you know the middle next to you (6B) is being used for seating? By calling and asking? Or, by making a dummy-reservation and looking at the seatmap?

If by calling, then yes - another 1P or higher has asked for the seat.

If by making a dummy-reservation - then the seat only looks taken because you are next to it and it is not available for anyone else to select!

Good luck . . . and even 6A with someone in 6B will turn out to be fine - it did for me several times.

JK-SFO