If is probably used only to preserve the computation power of the servers if that is done on server. It that is true here is your answer why they do it that way

If u look at the screenshots u can easily see, that the driver has the small Parthenon stile icon which signals Accelerated Training. The Commander Boetel does not recieve it. All information is available. For both crewmembers the personal Info tab is opened.

On top of that the battle result tab is opened XP in the line “Received” always represents base XP, and therefore base XP was: 627.

For all calculations it is important to know that WG always rounds down, eg: 5,3 = 5; 5,5 = 5; 5,9 = 5. Not nice, but this is how Credit and XP gain works in this game.