It is really that simple I think.

I've twice wanted row 16 A/K in Y (the bulkhead window on the long-haul 767) recently and as it was blocked on ba.com I called the gold line at T-72 who both times were able to put me there - but explicitly warned me that if someone booked with an infant between T-72 and the close of check-in they would get priority.

I was quite happy living with that.

Of course the risk is that you might keep your seat but that the seat next to you (B or H... or any of that row) is full of infants in bassinets.

(Thankfully on that trip I was op-upped to WT+ on both legs anyway but that's beside the point )