I just remembered something about the study I referred to earlier. I have got to find the damned thing again. As I remember it, since they did not want to simply end up with a discussion of the value of protecting the plate, they only included swings in counts at pitches that were actually in the strike zone. By eliminating swings in counts at pitches outside the strike zone they also got rid of differences in all hitters ability to judge pitches to be in the strike zone. That does skew the data. So for example, as you might imagine, the hitter's results when swinging 0-2 were worse in an absolute sense than their results when swinging 0-0. However swinging 0-2, hitters ends up swinging at a considerable number of pitches that are outside the strike zone even if by a little bit. As with everything baseball it is complicated. I can see their point. If they included swings in counts at pitches outside the strike zone then they would have simply ended up with a study that said "hitters protect the plate with two strikes" and their average generally sucks when they are forced into that predicament. I suspect they did not think taking four years of data to come up with that hypothesis was worthwhile to them.
They were really trying to come up with data specific to pitches in counts that were in the strike zone...in other words pitches that would have been called strikes had they not swung. They were trying to validate with data points that the more pitches a hitter sees from a pitcher, and the deeper into the count he goes, the better his chances of getting a good result swinging at a pitch in the strike zone. That does make some sense. The hitter sees more and more of the pitchers release point. He gets a better feeling about the sequence the pitcher is using to get him out and if he gets the pitcher all the way to a 3 ball count, the better his chances of getting a FB....maybe even a FB right down Main St.
I remembered at the time thinking that one of the things they were really trying to get at was the value of guess hitting, whether it really worked or not and whether the hitter generally makes a better guess the more pitches he sees and the deeper into the count he goes. I seem to remember that they did something with swings and misses with two strikes (K's) so that you could see K's separate from balls put in play. But. for the life of me I can't remember what it was or why they did it that way.
So to qualify my earlier comment about this study, swings at 0-0 pitches that were in the strike zone yielded worse results for the hitter than any other swing/count at a pitch in the strike zone