I, too, have played in multiple tournaments that have used the Rule. Sorry to rain on your parade, Apex, but as I've said before: The One Ball Condition is not what WGT is doing here.
from the USGA itself:
https://www.usga.org/RulesFAQ/rules_answer.asp?FAQidx=177&Rule=15
"When changing balls, the player is permitted to substitute a ball of another brand or type unless the Committee has adopted the One Ball Condition of Competition (see Appendix I; Part C; Section 1c). This optional condition (usually referred to as ‘The One Ball Rule’) is generally adopted only in events that are limited to professional golfers or highly-skilled amateur golfers. Generally, this condition of competition is not adopted in club-level competitions."
WGT does what it does here only because it was the intent not to allow choices to the players, something that was addressed by Mr. WGT years ago. It has nothing at all to do with the One Ball Condition of Competition.