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First, it depends greatly on the level of track athletes youre referring to.  If youre talking post high school/collegiate and up, and they are competitive at that level in the power/speed events, then they almost certainly are the former type of athlete we are talking about. The other guys have dropped out by that point.   

You can for sure see an improvement in the counter movement and run up of anyone, the problem is it doesnt help after a while and can even hurt some guys to try and go faster than they "need" to go.   Not picking on kingfish at all here, but have you ever seen him from an approach?  Thats VERY common as well with those type guys, lbss will be the same.  The longest run up they will benefit from will be a couple of steps at MAX, and even then some will lose height that way.

There are very little studies or anything other than theories, experiences, and anecdotal evidence done on this type of thing at all, its simply not that common an interest.  Some claim that the more muscular dominated movement pattern requires more time for the actin and myosin cross bridges to develop force.  This is why you tend to see a very close standing vert to running, or even higher standing in these athletes.  Tendons dont work the same way.  More velocity, better output.  This may not be 100 percent accurate, but it tends to hold true if you study which type of athlete youre dealing with.     

  One thing you guys are overlooking, which is a HUGE factor in kingfishs ankle dorsi flexion is he is purposely squatting on the front of his feet.  Even with weightlifting shoes on his heels come off the floor at times. This will drastically alter the perception of dorsi flexion in a normal squat with the weight on mid foot/heel.   Hes obviously adapted to this and his knees are fine, but trying to copy that aspect of his squat will hurt a lot athletes who are not Kingfish and do not have his proportions nor time spent  building strength in that movement pattern.

why'd you stop the front squats?

Is your sprint test a 30m or 60m sprint?  A 30m is hardly worth for unless your uncoordinated IMO... but it would make sense to concentrate if it was a 60m, would love to see how your training methods would work there.