I don't fully understand how we are ranked here, I'll trust OP but for example in the 2018 Platinum ranking I got 6 points in total so far and this year so far I have 1 Platinum. But on the first post in this thread OP clearly says that Platinum trophies are worth 12 points, yet I only have 6 points...
The platinum leaderboard has a different points system. In the 2018 season and overall ranking leaderboards, each platinum is worth 12 points. In the platinum leaderboards, each platinum you earn is assigned a point value based on how rare that platinum is.