Actually, did you actually read the article? They mentioned that the lanyard can cause a modification to trajectory (that would be a direct cause due to an air vest); the sound (that is a direct cause of the air vest); and again, the 1.7 times increase is not scaremongering because it is a clear increase when an air vest is worn. Use Occam’s Razor given all other variables being equal.
Now, let’s define “sever chest injury.” Does that mean crushing injury with no broken bones? Does it mean there has to be broken bones? In ANY quality epidemiological study, the parameter definitions are absolutely paramount in order to conduct the appropriate statistics. The list they provide in the BE study is impossible to measure using their methodology. And they claim in their results that it is likely an air vest will NOT prevent serious injury.