Color me confused.
1. When I choose from the Grey swatches, I choose Black 30% and I get a light grey. This is as expected.
2. Then if I use the Colour panel switch it to Greyscale mode, the same percentage works the opposite way. 30% gives me a dark grey. This is not how I would expect it to work.
3. On top of that, if I click on a color swatch to change something like text color or stroke and fill color for a table, the term is changed to say Greyness.
In my opinion, the only thing that's right here is #1. What's wrong about #2 is that the slider says Grey but really it's black, and when you drag the slider to 100% you're not getting 100% black or even 100% grey, you are getting 0%, or rather white.