Hi K, from memory it is to do with load shedding after engine start. If one engine generator comes on line first, knocking off the ground/APU, even if you start two engines at a time, it will load shed some IFE and galley power which then has to be re selected manually after more than one engine generator is available. It is just messy this way round so to avoid the problem switch off IFE / Galley first.