Perhaps some other mechanical engineers can chime in, but here are my thoughts.
First, I'm pretty sure he's not using his reference to the Tea Leaf Paradox correctly at all. The Tea Leaf Paradox, refers to a very unique phenomenon which occurs when the specific weight of an object relative to a certain centrifugal force create a state where the forces balance and the suspend the particles at the center of the vortex. (It's not really a paradox at all.) However, once the centrifugal forces change (crank speed changes), or the mass of the object change (oil particle size) then the balance is disrupted and the particles will no longer suspend. This is important to note because inside a crank case not only are the oil droplets varying in size/mass, but the engine speed varies wildly as well. Therefore it's almost impossible that oil would stay suspended in a "Tea Leaf Type Paradox" for any significant period of time. Therefore I feel as if the author is incorrectly stating the governing process. This, for me, severely hampered any credibility of what he wrote. What you really have is a cyclonic (like a Dyson vacuum) with all states of mass and centrifugal forces (crank speeds) which leads to a oily vapor mix (as he referenced as a cloud).
However, if you can overlook the fact that applies the wrong phenomenon to describe the oil cloud in a crank case, there are applicable statements and concepts in what he wrote. I believe that the crankcase scraper in actuality works very much like a baffle/separator plate/deflector plate in a centrifugal separator. In a centrifugal separator, high cyclonic speeds cause heavier particles to spin outwardly. If you can put a baffle/separator on the outermost edge, then you can capture particles. His referenced picture actually best demonstrates this.
For reference, here is a typical centrifugal separator:
In this way, the scraper is more of an oil baffle/collector, separating the oil from the air. So the question is, would this improve HP? While it's true that reducing the amount of free oil floating in the crank would reduce some drag, in my opinion it would be so minimal that it would result in negligible HP gains. Think about it, is it any harder to run in the rain than on a sunny day? Yes you are trying to push through each droplet of water, but it's significant? I think the baffle would help collect oil and return it faster to the pan, but again, it's a very negligible amount. Unless you need every drop of oil, your system is probably sized to compensate for this anyway. My take is this. Does it do what is intended to do? Yes, it should remove some of the oily vapor mix in the crank and return it to the pan. However, how much are we talking about? Very little. And is that enough to really make any difference at all? Not really. HP gains? Immeasurable. What it has going for it is that it is a passive device, it doesn't have any parasitic attributes to it; it's not going to hurt. It's like if I said, would washing and waxing your car help performance? One could argue that a smoother sleeker surface would contribute to less drag and air friction; but is it worth washing and waxing your car strictly for performance reasons alone?