Yeah, he writes some interesting stuff. There are others out there to follow, but, you also have to watch for the junk tips as well. Verify what anyone says or has written before it goes into any sort of head.
Jumping back for a second to our flow within the port, non-turbocharged vs turbocharged engines, our flow area will be roughly in the same portion of the port, in a general sense of putting it of course.
Here is the intake of the 7.3L IDI once again. I have highlighted the valve boss area in both the intake & exhaust. From the factory has some decent size to the valve's guide boss. I believe there is enough meat there to shape it more aerodynamically and hopefully produce more stable flow within the bowl area and not jepordize the strength to keep the valve operating in the position its supposed to. The boss doesn't seem to have much of a gradual slope into the roof of the port. Relieving the severity of this angle creates the better flow path into and through this part of the bowl area. The arrows I have used indicate the point of each side of our valve boss comes into the bowl. Could doing some material removal & radius work in these two areas benefit?
Seeing the exhaust valve guide boss in a highlighted picture as well, you can see the obvious. Going into and out of the cylinder, there will most likely be a generation of vorticies or 'turbulence' if there is immediate changes or of the like in the path. If we improve our exhaust flow starting at the face of the valve, between the valve curtain and seat along the short and long radius, around the valve guide boss. This brings us back to the thought of scavenging of our cylinder. Improved flow should decrease cylinder contamination from reversion on this end. If things flow well up to the turbocharger's capacity, reversion will be reduced without needing to test an tune anti-reversion techniques. There will be reversion on the intake side from the higher cylinder pressure compared to intake tract pressure. Intake air contamination may be reduced as well only if the back-flow characteristics are good. Flowing heads backwards can tell how easily reversion will be.
Looking down into, you can't see too much as far as good definition of the view of the exhaust boss, maybe it was the quality of the camera. Anyways, you could call the shadowed area the top of our boss from how the picture is taken. Again, any head you can do the same basic shaping and clean up as long as your port does not become 'out of shape' compared to how the port itself came.
Since we improve flow stability and capacity through porting (increase in velocities and CFM too) and cleaning up casting imperfections, we produce a stronger swirl action too. Now if you look at the 6.9, 7.3, Cummins 5.9 12V mills you see that the valves are positioned in the center of our cylinder/chamber. Since 2 valve cylinder heads influence swirl naturally, its best to maintain mixture motion in the center area which the valve positions and the piston crown influence this. I hope to get some ported pictures of something on here in the near future.