It apparently is a thing.
I won this SWAT match and I actually ranked down 7 points (2095 to 2087). This should not even be possible. While it’s true they had a platinum player on their team and it shouldn’t be worth nearly as much as beating a full team of onyx there still is no excuse for this to be happening. At worst, the match should award 0 points but you should NEVER actually rank down from winning a game regardless of if it’s a full team of champions against bronze, especially if this is going to be an issue every time I match a random plat when searching at high onyx since it’s not my fault I matched him.