I've tried a couple of different hypothetical 'what if this increases your drop chance' scenarios*, and noticed no appreciable change in drop rates. If there is some hidden RNG modifier it's not a statically relevant factor*. I'd honestly be a bit pissed if they threw something like that in without telling people. Variable force compositions and play-stiles would guarantee an uneven reward distribution more surely than a pure RNG system.
* Wiping out all enemy tanks, maximizing live turkeys at win, playing to PoC battle/time bonus score, fighting with more destroyers, rushing, ending with 10 gears.
** Given the small sample size it's a hard thing to test.