All this shows is that it's been a deliberate tactic of the Roosters to give away penalties when defending their own line since 2008.
You give away a penalty any time your defensive line is stretched or rushed inside the ten. It gives you the chance to reset again against a set start, plus it frustrates the opposition because they never really get a roll on. Eventually, if they've had enough tackles with the ball in your 10 and they haven't scored, they start to feel the pressure of the whole situation and then they start to take stupid risks because they feel that they really should have scored with all the ball that they've had.
Roosters woke up to this tactic much earlier than all the other teams but quite a few of them have started to copy it now.
If you broke down penalty stats and excluded penalties given away when defending your own line, I'm sure the Roosters would compare much more favorably with the rest of the competition.