To what extent is this all related to the fact BA have an uncompetitive 8 across layout in club? (I accept the flat bed was market leading, but 8 across in J was a blast from the past). This move may have been designed to help BA maintain market share as people like CX roll out their new J products.
After all, many carriers don't allow you to preassign in Y and BA do allow you to assign in F regardless of status.
Just a thought...