Ben,
David's stat isn't too broad, it's too narrow. It doesn't account for all the variable conditions surrounding a green excluding the bunkers. He hasn't posted what the save percentage is for areas other than bunkers. And, I would bet, that from week to week the turf varieties, heights, grains, etc. are much more difficult to standardize which would make that stat much more of a moving target.
Besides, there are no stats that SPECULATE what would happen if bunkers were less pristine and predictable...because, on Tour, week after week, the sand is likely as predictable as green speeds/ uniformity.