over 2 years ago - Mandy - Direct link
Grades are not used for matchmaking, grades that you can see show how much time someone has played in a month, not their skill level.
Matchmaking is done on an MMR/SBMM system which is hidden.
Your MMR doesn't decrease if you take a break from the game for a little while, which is probably why you are noticing a disparity at the moment.