Really, the only purpose to document all these settings is for statistics. To show that more Nexus screens come with x-color tint than y-color. Even then, you're trusting people to know what white and gray are supposed to look like. I've seen how most people set up their TVs - they're usually wrong.
There isn't a HUGE variation in the differences. Each screen isn't a special snowflake. There's a relatively small, finite number of different screen settings that work for all screens.
This will give people a narrowed-down list to try first instead of spending hours experimenting.
It doesn't take hours, it's a pretty easy process:
Color multiplier is white balance, which also affects overall color tone. Get two things: a blank white screen, and a pure black screen with white text (settings is easy if you have gradient disabled.) Use these, and go with what you think white should be, unless you have a good reference or a calibration tool. For example, I dropped red/green because my screen was too yellow stock. I then found that I could still almost see the individual red pixels sticking out of text (best way I can describe it), and looking at my home screen felt a little too "pink", dropped red a little more until it looked fine.
Next is gamma/offset/whatever which is the adjustment of everything in between white and black. This one can be trickier because grays can easily look too red/brown, too blue, too yellow, etc. and on these screens the gray balance will change depending on brightness. Yes, sometimes drastically (see: purple tint) This can be a pain if you need to lower greens because green can't be lowered (the screen goes nuts), and the colors don't scale the same, so if you increase red and blue by the same amount one will probably be stronger than the other.
Just from my experiences. And yes, each screen is
a special snowflake. Most people are just happy enough with canned settings.