Torsion bars shouldn’t be run with damage to the smooth, constant diameter part of the bar. The “active” part of the bar starts about half way down the radius from the hex to the constant diameter of the bar. Nicks in the end of the hexes like don’t see the same loads.
But yeah, that looks like a casting flaw. Maybe ask @PST?
That looks as though it was a flaw during the forging process. It will not affect the performance or integrity of the torsion bar. at all. You are more that welcome to send it back for exchange if you would like.