Yes, but this has been the case for years - and is the case where the law of unintended consequences hits the customer directly. BA allows you to select seats early. You select them as close to the front of the plane as possible, because you want to board and deplane quickly, or because you prefer an exit. You like the flexibility offered by BA as part of the package they provide for your loyalty.

A separate set of operational processes means that the curtain needs to be able to move - directly impacting the most coveted seats chosen by the airline's best customers.

I am sure BA never intended this to be the outcome and is the result of silo behaviour. You - as one of their best customers, aren't notified of any seat change and end up in 25B, auto reallocated.

It used to be more annoying when the seats further forward had more legroom - perversely now that's not the case any more, I'm less concerned about shorthaul seat shifting (unless I end up in a middle seat)