I don't believe it is the pressure from the water flow that is giving that effect. First, the pressure involved is extremely small, so its effect will be extremely small. Instead, I believe the water flow against the ceramic disc is simply removing the bubbles as they form, before they can build up into larger bubbles. Similar to when you use soap solution to blow soap bubbles - if you blow carefully so the soap bubble stays attached to the wand longer, the bubble will grow bigger. This is the opposite effect - it removes the bubbles from the wand -ceramic disc- before they can grow bigger. I suggest we now call this the "JeffWW Effect".
This is not to belittle the idea at all. In fact it is very good information. We normally put the diffuser where the stream of bubbles coming out can be blown around the tank. This idea is to put the diffuser where the water actually blows on the disc, preventing big bubbles from ever forming, and giving a "mist" of fine bubbles instead. Simple and very effective, and very embarrassing to those of us who didn't think of such a simple concept. It's like when Newton got hit on the head by an apple?
Thinking about this some more, people use a piece of chopstick in the end of the CO2 tube to diffuse CO2. If that end was then stuck into the filter outlet fitting, as shown below, would we get much finer bubbles, due to the JeffWW Effect?
One more thought: this is why a Mazzei venturi works so well as a CO2 diffuser. The CO2 enters at the throat of the venturi, where the water is moving very fast, so it shears off the tiny bubbles before they can even become visible bubbles.