Following the above post, I received a reply from simonthebeetle via email, when I checked who he was it appears he is a Champion, possibly also an employee of WGT. who gave the following breakdown of how to change tiers:
Subject:Requirements for Tier Promotion
HACK to AMATEUR
Minimum Ranked Rounds : 5 / Average Score : lower than 100
AMATEUR to PRO
Minimum Ranked Rounds : 10 / Average Score : lower than 80
PRO to TOUR PRO
Minimum Ranked Rounds : 20 / Average Score : lower than 72
TOUR PRO to MASTER
Minimum Ranked Rounds : 25 / Average Score : lower than 67
MASTER to TOUR MASTER
Minimum Ranked Rounds : 40 / Average Score : lower than 63
TOUR MASTER to LEGEND
Minimum Ranked Rounds : 50 / Average Score : lower than 61
LEGEND to TOUR LEGEND
Minimum Ranked Rounds : 500 / Average Score : lower than 60
TOUR LEGEND to CHAMPION
Minimum Ranked Rounds : 200 / Average Score : lower than 59
CHAMPION to TOUR CHAMPION
Hypothesis #1 : Exclusive Personal Invitation from WGT
Hypothesis #2 : Upon reaching L300*
(* Based on the description shown in the mobile version)
It is of course laughable, but also shows that it clearly a random selection when you move up!
I took a random selection of 35 WGT players all at Tour Pro Level their average scores ranged between 67.56 and 101.37.
This shows that the players selected should actually be ranked between Hack to Tour Pro.
It would appear that there is no clarity in the tiering of players!