The Northern Illinois Men's Amateur Golf Association (NIMAGA) has had a 12/24 pace of play policy for years. As is the case with the policy described, your group must finish 12 minutes behind the group in front of you, or 24 minutes behind the group in front of them. In actual effect, the policy is an absolute nightmare.
The last time I played on their tour (it was '03), the two events I played took 5+ hours. These guys mark 2 footers all day until at least the 16th hole, and then literally run the last two or three holes in order to not get penalized.
My first NIMAGA event -- going back 12 years or so -- was at a small municipal tract in Mundelein named Countryside. They have two courses, neither of which is that interesting (but playing tournament golf remains enjoyable). The 16th hole is a par-5, reachable even by shorter hitters, so after arriving at my ball, my group waited for the green to clear. One of my fellow competitors hit his shot, and when I looked up, I saw the group which had just left the green sprinting up the hill on the next hole (an uphill par-4). The group in front of them could be seen sprinting down the hill on the parallel 18th hole. WTF? Oh, that's the "NIMAGA trot" I was told. They do this all the time. Play/WAIT all day, and then run the last couple of holes to make up any ground to avoid a penalty for slow play.
On our Weekly Challenge tour, each group gets a pace of play monitor (the starter attaches it to the bag of one of the players in the group)which tells you throughout the round where you are supposed to be (4th tee, 5th green, etc.). Our marshals check the monitor, and if you're behind you get placed "on the clock." Focus on the 12 minute interval at the end of a round is a recipe for disaster. . . unless you enjoy 5 hour rounds of golf.