Hextech chests don't seem to be coming in as promised anymore

According to the notes on the site and prior experience, you're supposed to get a chests under the following conditions: Somebody on your team gets an S rating You haven't gotten all the chests you can based on the time limit (1 chest every 6 days) You're playing a champion you haven't unlocked a chest on yet for the season

I've met all these conditions twice now. The first time I thought maybe I didn't get it cause our team lost even though we got an S. But I just won a game as Maokai who I've never gotten a chest with while Yasuo got an S rating and I have 1 chest available as loot. I did not get a chest for that game.

Can somebody tell me what's going on? Did Riot change the requirements and I didn't catch it?