Kohler CH20-64510 Does the exhaust valve need a valve stem seal?

Good Day All! I was talking to a friend and the subject of Kohler engine rebuilding came up. Last winter I rebuilt the 20 HP in my Grasshopper 720k, and the parts only came with 2 valve seals. So I just picked up 2 more and rebuilt the engine with valve oil seals on both the intake and exhaust valves. Runs Great! Been using it all year so far. My buddy says I need to remove the valve stem seals from the exhaust valves. He says the small amount of oil is needed to cool the hot exhaust valves. My repair manual wasn't much help on this subject, so I'm here to ask the experts! What do you all think?

Some engines have them others don't. The reason behind the seal on the intake is because the vacuum create by the piston on the intake stroke can pull oil around the valve stem.