Actually, WGT is following guidelines furnished by the USGA for settling ties without a playoff:
http://www.usga.org/handicapping/publications/Settling-Ties-In-Handicap-Competitions/
"If the Committee decided that a play-off of any type wasn't feasible to determine a winner, then matching score-cards is the next-best recommended method of settling a deadlock.
How is this accomplished? They could determine the winner on the basis of the best score for the last nine holes. If the tying players have the same score for the last nine holes, they check the last six holes, then the last three holes, and finally the 18th hole.
If this method is used, one-half, one-third, one-sixth, or one-18th of the Course Handicaps should be deducted. Again, fractions of one-half stroke or more should count as a full stroke; any lesser fractions should be disregarded. If the conditions of the competition provide that ties shall be decided over the last nine, last six, last three, or last hole, then the Committee should also provide what will happen if all these procedures fail to produce a winner. "
Since WGT doesn't use a handicap system the ignore the Course Handicap factors in the above method.