Perhaps it's because all three players don't give up hits?
Chris Young - SP
Durability should be low for CY, but he's a fly ball pitcher who allows about 7 H/9.
Hong-Chih Kuo - RP
Despite his disastrous 2011 season, he still gave up less than a hit per inning pitched. His H/9 before 2011 have been in elite territory. He is another fly ball pitcher.
Jason Isringhausen - RP
Hmm, another fly ball pitcher, I'm beginning to see a pattern, ground ball pitchers have higher H/9 while fly ball pitchers are the exact opposite. At 6.9 H/9 last season and 7.49 H/9 for his previous three active seasons before that, that's very good.
For comparison's sake, elite pitchers Tim Lincecum was at 7.3 H/9 last year, Mariano Rivera at 6.9, Clayton Kershaw at 6.7, and Justin Verlander at 6.2. Mediocre pitchers Jason Hammel was at 9.2, Kevin Gregg at 8.7. Average is around 8.5 H/9 to 9 H/9, while the games lower-tier pitchers are above 9 H/9 (over one hit per inning).