Sounds about right to me.
Any runner that is training to improve their time in the marathon is always running along the knife-edge that separates increased performance from increased injury.
I know this from experience.
It is the nature of racing marathons......always has been.......always will be.
Are these results biased by the fact that those who suffered more serious injuries in preparation for this marathon were not present be be counted in the study. As they were non participants due to injury?