I'm not saying this is the case here, but one thing to consider is that an extra blocker does not always result in fewer sacks. If you had advanced analytics to see how many receivers were considered on a given play, I would expect extra blockers to increase the amount of receivers that get a look, on average. But remember, for every extra blocker you have, you have one less receiver that needs to be covered, which allows for more coverage on your other receivers. All that to say that I wouldn't necessarily expect extra blockers to equal fewer sacks.