I only know of a few examples which is far too small a sample to go by.
If you can collect a wider range of people who are confident coin room play was the determining factor and then piece together their playing frequency, room participation, coin earmings etc, you could get a better picture of the criteria wgt is using. Right now, we can only loosely speculate at what some of those factors are.
Some of the TW crazy clubs likely have a fair number of coin room promos start there.