I don't find this speculation about particular training being contributory to these injuries, compelling.
Ok, so Powell's group does this. That might account for Powell. Now you're saying that Bolt was doing something like this...why would Bolt convert to a training method that produces more injuries and inferior sprinting? And what about Blake and Jeter, were they also converts to this kind of training and "dangerous" transition?
IMHO--IMHO--it has more to do with PED use than anything else.
Who have been the most glaringly suspicious sprint athletes over the past 5 years?
In no particular order, Bolt, Blake, and Jeter.
Who has gone down?
In no particular order, Bolt, Blake, and Jeter.
Powell is a wildcard. He is unreliable, unknowable. That dude has problems that are bigger than training.
BTW, that kind of training has always sounded to me like bunk. Sleds require very high--the highest--forces, but applied over a longer time, with slower cycling, and less training of time-to-max-and-back-to-zero. Similarly, doing 400-type stuff trains the muscles at a lower cycling rate, and worse than that, involves as you say "exponentially less force" at the same time.
Think of how a ham blows. It never blows on the first, second, or third step out of the blocks. Many think this is due to it not being used as much during this phase, but it is not really "how much" it is being used, but "HOW" it is being used that I think is the important thing.
On the start and during early acceleration, there is much less recovery action than there is in mid/late acceleration and top speed. Later in the race, the ham must stay contracted for a longer period of time, which leaves less time for back-to-zero--or if you prefer to think of it as a higher-power application and then a coast for recovery, it has the same amount of time to come down from a higher force application. Either way, it amounts to less time for recovery.
If this ability to quickly cycle and thereby permit recovery is not trained (like happens when you do sleds or 400's), fatigue builds up in the muscle with each contraction--and after a few of them, it passes the critical point and the muscle fails. If you are sharp and disciplined, you can feel it coming, and shut it down just before actual tearing occurs--but this requires substantial discipline, especially in a race situation.
Look at the structure of the workouts you did when you did NOT get injured in transition--shorter stuff, probably with faster turnover/cycling. Practicing quicker cycling also trains the neurology to be co-ordinated at that speed, something you also won't get from sleds and 400's...or even potentially from hills, for that matter.
However, having said all that, it is extremely coincidental that they have all gone down in the same year, at the same time of year, with the same injury. Granted it is a common injury.
The natural question is, who else has been training like this, and therefore the next likely candidate to go down, according to the training theory?
According to a doping theory, all the choice spots are already filled...who would be next on the list? I'm not sure.