I think this is not a very good study and that it appears to conflate a correlation with a cause-effect relationship. I do not see how the position the gun is carried in could possibly affect the decision to shoot. Therefore I think there is some other factor that is affecting both the decision to shoot and the decision on how to carry. My initial gut guess would be a matter of training since both decisions are made based on training....Erick Gelhaus’ talk about ready positions and “mistake of fact” shootings.
He reviewed many recent studies about the use of different ready positions affecting shooter ability to make correct use of force decisions. The high ready (gun near face, muzzle pointed up) is perhaps 0.1 sec faster to get gun to target than lower ready positions, but in well designed experiments, shooters using the high ready position made 30% more errors in shooting decisions. On the street this translates to “they shot people that should not have been shot”. Erick made the argument that lower ready positions sacrifice very little speed to provide significant reduction in unjustified use of force.
It is an interesting correlation, but it really means we need more research into it.