I'm not ready to believe the article is technically wrong so I wonder if someone can explain the idea or maybe contact the author for an explanation?
It is not likely that Harold Merklinger is wrong, but he did make a remark that I find puzzling.
For instance, he mentions "Using Adobe Camera Raw or Photoshop to "fix" the fringing in one part of the image makes it worse in another". To me it sounds like he didn't add some canvas space to the image before applying the otherwise centered corrections. I find that hard to believe, but I have no other explanation.
He then mentions: "We apply full forward lens tilt. This brings the plane of sharp focus up just under the camera just six inches below the lens in fact. The angle the plane of sharp focus takes with respect to the film/sensor plane is now controlled by where the lens is focused. With the lens focused at infinity, and with the film/sensor plane vertical, the plane of sharp focus will angle slightly downward away from the camera, just at bit below the horizontal plane". That is mathematically
impossible when the sensor plane is indeed vertical
AND focus is set at infinity on the lens! However, when one sets focus 'beyond infinity' on the lens, then a virtual image is created and the tilt allows to focus on that.
The tilt also shifts the entrance pupil of the lens a bit in the direction of the tilt. That may be the cause of the diverging verticals he noticed, and it's a useful observation indeed.
Cheers,
Bart