From wearing regular ones (okay many years ago working in wood sort of mills/production but not long either) I'm not sure the divot would make much a difference if proper clearance from sides to the inside harness, though guess may force impact in a way not intended for proper safety gear.

Still doesn't seem quite right to me, cause you wouldn't want your head knocked to a side if the brim was hit.

Probably a reason they were never designed in that way.