Call me an old cynic but its about marketing consultants making a pile of cash for their normal feat of making silly suggestions with no rationale behind them.....
It would appear that the manderins at the top end have decided that 'Consignia' conjours up a negative image, wheras 'The Post Office' seems cosy and solid, so lets go back to that. Everyone knows you can call an ass a horse, but it doesn't shorten its ears - Incitatus may wonder about being cynical, but there's no disputing the logic of his answer.