I have a Avios-issued ticket for CX HKG-SGN Y and still hanging onto my JL OWS.
I had to call into BA to change my FQTS. On the day of issue I had to then call into CX to do my seat selection (row 45, based on EF, see below).

I can do it online now, but only exit row.
I called in, and I was given the choice of exit row, front row (row 39 on a 33P) or any row in between (I picked row 40).

Side note: EF still shows all rows 39 to 44 as blocked. This is confusing as.