Hazed,
About the WEP temperatures:
Basically HT implied there were, within the different possible settings out of the factory, by the ground crew, in flight, for how much wep // how long // etc many plausible models to choose from for each plane.
So it's probably more complicated still than the reasons behind decisions like no AUX tank till 75% global fuel for P51D yet AFT/WING tanks of 152 filled even at 25% global, or that the fuel types used differ from each plane as well.
Probably same story as putting all planes in same cockpit units of measurements so as to kill 50 birds with one stone: mph/kph-etc misunderstandings in MA coms, no need to rememorize cockpit instrumentation from plane to plane, etc.
As for features that just dont make sense like the 152 seemingly not having a GM1 turned on, when it was pretty much the purpose of the plane design, then who knows? Maybe they at HTC don't have information to model it correctly like they don't for the A20 bomber rear bottom turret art, maybe this, maybe that, shake an eight ball.