I had the email in the middle of the night - a 777-200 ER for a 777-200ER with 5 rows of PE and not 3! It's only when you did deep, you realise that there are 6 or so 777-200 configs. The LGW old and densified I get, the no first I also get - but the other configs bewilder slightly. I get that having a number of configs they can match supply with demand in various classes. But having several iterations must mean occasionally they operate the wrong config when they run out of the "right one" - whatever that is!
In my case, I've gone from 24 to 40 PE seats overnight blowing any chance of an involuntary upgrade - I assume a surge in demand in one class has changed the config unless it's a predictive maintenance cycle. Still - at least I got the email - two actually, 2 mins apart. No harm done, a first world problem, and some proactive info from BA!