That's because it doesn't say that outright
. It's already a giant wall of text, so it's assuming the reader has a basic understanding of the technicalities involved in stuff that isn't directly related to the behavior of the CLI itself and/or of FBInk itself.
The API doc, on the other hand, delves into the guts of things (e.g.,
this would be the relevant bit, as well as the bit about AUTO that explains that flash + AUTO means GC16 in FBInk. There are even more details about that particular design choice in the code
.)).
When in doubt, check the API doc, it's much more detailed, and much better contextualized
.