So you can get 2 sinnoh stones from a single battle
Was just doing PvP for me and my girlfriend, she got none from the 3 battles with me, but then got 2 from her battle with Candela.
We both were shocked. No idea that getting two from a single battle was possible.
Answers
I'm pretty sure it's all RNG, and I haven't seen anything that provides enough evidence to say otherwise. I've seen people's teams get absolutely obliterated in PvP, and they get better rewards than the winner does. On the flip side, I've seen people sweep an entire opposing team with a single Mon, only to get the lowest amount of dust as the reward.
While I'm not always the biggest fan of RNG, I can understand why Niantic didn't want winners getting better rewards. Having equal probability keeps casual players incentivized to battle even if their opponent has many more optimized Mons. It also prevents multi-accounters from battling their alts and having said alts throw the matches in order to reap better rewards for their mains.