TL;DR: When two players resign immediately after each other, leaving one player left, the remaining player doesn't seem to get the +20 point bonus for being the last player standing
I neglected to take a screenshot of this, but here's what happened:
I was playing Green. Blue (across from me) resigned early with 0 points. Gold (to my right) grabbed Blue's king and ended up with a pretty big lead. I ended up in a vicious battle against Gold, while Red played defensively. Eventually, both Gold and I were pretty depleted in material. Gold was still well ahead of both myself and Red on points, but basically had only king and pawns left, and so resigned, with 53 points total. At this point I had 32 points, while Red had 24. However, I had only a couple minor pieces left, to Red's more or less full army, not to mention that Red was one move away from capturing Gold's king. Given that I would surely lose to Red 1-on-1, and had little hope of capturing >20 points of material to pass Gold's score, I decided to resign immediately after Gold's resignation. To my great surprise, I ended up in second place in the game, with the final scores at Gold: 53, Green (me): 32, Red: 24, Blue: 0. I was very surprised that Red didn't get +20 for being the last player standing. I'm guessing this was because both Gold and I had colored kings on the board? In any case, this was pretty unfair to Red, since s/he should have finished in 2nd place with 44 points for being the last player standing.