Tahm Kench will give you an S

So everyone knows Tahm Kench is fantastic. So I've been playing him as a support. A couple games have gone well, and of course, a couple haven't gone so well. I have gotten an S rating on Tahm Kench everytime I've played him support. Last game, I was probably my team's weakest link (granted I was the support). Still an S. How many games have I played him you ask? Only 5. But still, 5 games with one guy and getting an S everytime. Plus I'm relatively new to him.