If the Y-1/1 would be devalued, we would very likely see an increase in injuries.
Just a quick glance at the season ending injury list, indicates to me this change would be a bad idea at this time.

On the other hand reducing the Y-1/2 to 9.9 might be more appropriate.
That vault has front landing risks similar to Handspring-Fronts.

It would be interesting to know exactly what skills were being performed when the injuries occurred.