The definition of overspeed is tricky. For example, running flying 20s off a full relaxed run up will often result in a segment that is faster than is possible in a race (up to that point, at least) because the 20m segment is not compromised by the acceleration. Assisting in the acceleration can enhance the quality of the 20s further by making the approach to maximal speed easier.
The trick is knowing exactly how to keep the athlete in rhythm through the acceleration and when to let go each time, every time, with no mistakes. This requires trust in whoever controls the assistance.
I know it scares me and I’d rather rely on a tail wind. The marginal gains with assistance allow you to advance the speed a bit faster, which might be more of an issue in a L-to-S type approach where less time is available for this overall.
The other issue is athlete level, as the higher to performance goes, the less room for advancement and error there is. Most collegiate athletes enter a system with a fairly significant margin for improvement, and, if all goes well, leave it with limited room for more, so that would imply flexibility on the part of the coaches if the injury rate remains low.