Can't recall why, but the rule was changed in 2011. Prior to that, the rule required that there be a kick from a scrimmage kick formation for a low block that occurs PRIOR to the kick being illegal. I wish they would put that rule back in place. Team B can't know when a "quick kick" is coming, so they should not be held to that standard. When Team A is in a SKF, then Team B has 'notice' that a kick may be attempted, so they should avoid blocking below the waist from the time the ball is snapped.
At the same time, though, if Team A is in a SKF, but they know they are going to run or pass, then they have the advantage of knowing in advance that they may employ legal low blocks while Team B has to wait to see if Team A kicks the ball before they can know if they may execute an otherwise legal low block.
A possible solution:
Return to the requirement that the kick must be made from a SKF. But, for blocks that occur before the kick to be deemed illegal, require that the ball be kicked before the potential kicker has moved more than 2 yards in either direction from his position where he receives the snap. If either team commits a low block before that, and there is a kick before the kicker has moved more than 2 yards to either side, then it becomes a foul. If the kicker moves more than 2 yards to either side before he kicks, then low blocks (otherwise complying with the rules) up until the time the ball is kicked are OK.
This would retain the safety provision of the rule when Team A kicks "straight up" (no trickery or deception), yet allows Team B to play normal defense if Team A fakes the kick and runs/passes, or runs before kicking. Team A only has a very brief advantage over Team B, in that, if they run or pass from this formation, Team A would know they can BBW legally for the time it takes the potential kicker to move laterally 2 yards. After that, both teams would know that they can BBW until the ball is kicked. Once the ball is legally kicked, everyone knows that BBW is illegal.
Just ramblings of an old [your choice of words].
Robert