The two handers high speed, high rev rate release doesn't read the front of the lane, near as much as what most traditional bowlers ball does. It's much easier to create the proper axis tilt on the ball when your thumb isn't in the ball. Their ball reaction doesn't see the early hook in the heads, so their moves aren't as sudden and quick. Combine that with the fact that the high powered release and ball speed will also break up splits easier, and they aren't shooting at the designer spares as often.
Back in the day when guys like Dennis Jacques, Marshal Holman, the higher rev guys of the 80's, would over hit a ball, they payed the maximum price for the miss, that is unless they got it to cross over. You can add Bob Vespi into that category, in the early 90's. Granted, there were weeks that their ball would lay, and strike, and weeks it wouldn't. There was "next week" in an effort for all styles to have a look, and have a chance to really have the best ball reaction of that given week.
In today's game, the slicker lanes and lane oils and the even faster ball speeds with higher rev rates, don't pay the price as often for missed shots, so it becomes an illusion that they are better spare shooters, and more accurate.
When you only have so many tournaments a year to bowl, the advantage is magnified.
Kegel did a study a few years ago on lane topography, and ball speed was the biggest factor in ball reaction seeing the differences from lane to lane. Higher ball speeds, although affected, didn't show as drastic of a difference from lane to lane, as a slower ball speed bowler will. They also concluded that straighter trajectories through the front of the lane also was more beneficial. Bottom line, if you can produce a lot of speed, revs, and have a cover stock that keeps angles in front of you, you are going give yourself the best chance of maximizing your scoring potential from lane to lane, and from pair to pair.
I didn't include Belmo in the above examples of guys, as he has clearly refined hid game, and actually posts shots. But I will ask this, do you think he was really "hitting" the ball when he was being tested on C.A.T.S.? Do you think he was throwing the ball with loft and high revs and axis rotation like he does when he gets in to 6th and 7th arrow? This is when the two handers excel. They can get the ball to corner, or they can zone back right, and throw urethane, and still get it to hit.
I don't think it's the same as the power players of the 80's.
Here is a perfect example of what I'm talking about. Watch how high the ball hits the pocket and strikes. That's big four for most everyone else:
https://www.youtube.com/watch?v=cEI69YFm9uo