I’m sure that this is also in the instructions, but it’s probably worth adding that under this workflow with “Preserve (RGB) Numbers” enabled, you don’t specify the ICC when you print via Print Tool. Typically you’d edit the image in Grey Gamma 2.2 or AdobeRGB, soft-proof, and leave it that way for printing.
The alternative workflow is to leave “Preserve (RGB) Numbers” unchecked, soft-proof that way, and then do specify the ICC when printing via Print Tool. This worflow is what you’d typically use for colour printing. It’s not usually recommended by IJM for Piezography because converting to the ICC “crushes the shadows” and you risk losing shadow detail, but it can be effective for some images without deep shadows, or at least without detail in the deep shadows.
I wrote a tongue-in-cheeck blog article about the differences between these two workflows a few years back, prompted in part by a hard line that Jon ran against ever using the ICC when printing. I get the sense that the IJM line on this has since softened.