From my understanding, Tour Champion was never meant to be "earned" in the sense of actual achievement...ie, a certain number of ranked rounds and low average. It's an honorary title, based solely on invite by WGT. The criteria one needs to meet was never explained.
Since its inception, there have been only two people elevated to the tier. Icon and "Phiber", co-founder of ABoB CC, who was awarded the title posthumously.
Like many ideas before it, the concept of TC seems to have floundered.
The above is to the best of my knowledge. A moderator is better positioned to address this. Perhaps Icon would be so kind?..:)