My adjustable sights tend to cause others to have a higher POI than I do, I'm not flinching...it's just the way my eyes work. I shoot both eyes open. So with my fixed sight firarms if I have a low POI, I'll use lower velocity rounds and that will usually solve the problem.
If he's grouping is tight and consistent, he could have the front sight lowered a bit...but I'd try different ammo first. I handload so it's easier to match the round to the gun.
"And remember, Abraham Lincoln didn't die in vain, he died in Washington D.C." - Firesign Theatre