Could there have been a connection? Mere fashion and consistency of grip between Open Class and Limited Class guns *could* explain why those same top-gunners don't seem (I could be wrong) use the frontly finger when shooting non-comped pistols...
I don't know (and don't really care) about target shooters, but I don't think you'll find many combat instructors teaching finger on the trigger guard.
Many Sigs are designed with the same type guard.
Seems as if someone at some point thought it was a good idea.
Yep. Somebody thought so. Doesn't mean they were right.