Honestly I think there certainly is something this season. It's just weird. I am a U21 manager as well, and while I don't track my prospects every week, but yes, there has been an increase in injuries not only in my own team (2 players injured so far, not counting those who get injured in game only, 1 injured up to 2 weeks, and I have a level 6 doctor, so imagine how bad the injury was), but in the U21 as well (fourth injury of the season, the most I've had in the U21).
I did bring it up in a thread earlier this season:
(311333.1) and despite two other players noticing a bump in their injuries, I kinda wrote it off as bad luck as the sample size was too small. But now I think there might be something to it.
Sadly, I doubt we will actually know for sure.