XC70 curtain airbag

I've noticed that NHTSA's safety ratings for the XC70 are good, but they state that the curtain airbag did not provide any protection, since it deployed on the dummy's head. It seems this has happened in the XC70 tests for the past couple of years.

Does anyone know if there is some sort of problem/defect with the curtain airbags in the XC70/V70?

Thanks