Obscure rules, limiting rules, and the Super Bowl

Two items following on my post on the rules discussions following the Super Bowl:

First, here is a nice discussion of the fair-catch kick rule that the Niners might have tried to execute to tie the game had the Ravens punter shanked the kick. The author describes the rule as vestigial, a throwback to rugby's "try from mark" rule, which rugby subsequently eliminated, as did college football. But arguably the rule remains necessary to maintain a more even balance of costs and benefits on an intentional safety, by giving the trailing team another weapon with which it can counter the benefits the leading team gets from the intentional safety.

Second, a commenter to my prior post raises the situation that may have occurred in last year's Super Bowl: The offense needs a touchdown to win or tie while the the defense wants to stop the touchdown and run time off the clock, so the defense puts extra players on the field. The extra players obviously give the defense a better chance of stopping the offense on the play. And while the defense will surrender five yards and the down will be replayed on the penalty, time has run off the clock on the live play, meaning the offense will get fewer plays to run.

This seems to meet the three features that necessitate a limiting rule: The defense has an incentive to do something we ordinarily don't expect; the defense is in control and the offense cannot counter (because trying to score against 12 or 14 is going to be exceedingly difficult); and the cost-benefit disparity has increased dramatically, because the offense is going to run out of clock on wasted plays.

And recognizing this, the NFL enacted a limiting rule: If the defense has 12 men on the field and the extra players are not attempting to get off the field, the play is whistled dead on the snap and the clock stops (if the defender is trying to get off the field, the play is live, since the extra defender does not hinder the offense). This eliminates the advantage to the defense--it cannot use extra defenders to stop a play and cause the offense to waste time because the clock stops--in turn eliminating the negative incentive for the defense.