Twisted Treeline no Mastery Tokens?

I just finished a game on Jayce (I am mastery 5 on him) on Twisted Treeline, and was excited to get an S+ rank. I did not, however, receive a mastery token. It was my understanding that all S-, S, and S+ ranks were awarded mastery tokens, with no RNG in control. Is that not the case? Or is is just that Twisted Treeline does not grant mastery tokens despite the fact that it finally gives mastery points?