Seems to me the exhaust exiting the cylinder would just be flowing the path of least resistance. both ports open and close together, so any obstruction is just that. An obstruction. The more open the path the more flow can be achieved.
 
It's not that simple. If it was everybody would be running 3" dia. pipes and making maximum horse power. When the exhaust valve is closed there is no exhaust gas moving behind it so with a huge pipe the velocity is low and the flow almost stops then has to restart when the valve opens again. The exhaust gas has to pressurise this slow moving column and get it moving again. With a smaller dia. pipe the gas is moving faster and never stops, in effect it helps suck the next pulse out of the cylinder.
A huge oversimplification that lacks detail but it helps to explain the basic principle. Everything on a street bike is a compromise such as a small exhaust giving excellent low and mid range torque lacks the flow needed for top speed work.
 
I understand what you are explaining, but the original question was about the intrusion in the head and exhaust. Its not much, but if therr is an improvement in removing it. Then while I'm in there I want to do it.
 
My thought is the nibbs continue the round aspect of the port just enouph to keep the exhaust gases swirling correctly so keep the flow as needed for the high torque in the low end. Just like the short velosity stack are needed in the factory intake.
 
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