Possible hole fix - Drip those holes away!

[Feign]

Now maybe, they just printed things until there were no holes, or maybe the problem is simply a question of Rylan printing with walls that are too thin in problematic areas.

Both of these are likely. Also, the Hardcotton printer is able to raise and lower the resin level as well as dwell on a layer as long as it needs to, meaning it can print the solid pieces, spending as much time as needed on each layer. The Peachy has a time limit for each layer, necessitating the hollow shell printing in most cases. Though it printed the Rook solidly, and there were definitely no holes in that. If he had printed the Yoda with three layers in the shell rather than just one, I'm pretty sure there wouldn't be any holes at all and still have all the resin economy you could want.

I wouldn't call the Hardcotton printer a Peachy Clone, as the only similarity it has is being a top-printing SLA machine.

I mean that it is like total internal reflection with a laser. The waves that I am talking about here are sound waves. I am just saying that how the sound waves travel here is similar to light waves, so that it is easier to visualize. So if you create a sound wave in the liquid that is heading toward the surface, you can kind of think of it like a laser shining up at the surface. If the wave is normal to the water then it will pass through into the air (without creating any surface wave at all). If the sound wave is at a significant angle then instead of passing through to the air it will cause a surface wave (where as if it were a laser the light will reflect instead of causing a surface wave). So I posted the video of the laser just to give an intuitive sense for how the sound waves are working. The stuff in the video involving a flashlight and after is not relevant. Let me know if I am still unclear.

The problem here is with your core assumptions.
First, a wave will only remain stationary where it is exactly 90^o to the fluid's surface, any angle at all will cause a wave to propagate along the surface. This is because viscosity carries energy between molecules in a liquid even if the direction of the force itself doesn't pass between them.
Second, mechanical waves in a liquid or solid propagate radially, similar to how light waves propagate from a light bulb. There's no way that I know of to form an actual cohesive mechanical wave through a fluid (though there are ways to fake it through amplifying and cancelling waves, but those cause all kinds of incidental vibrations that you don't want.)