EWMH specification doesn't say windows of type "dock" cannot be moved, but docks & WMs assume this

[ornx]

I am implementing EWMH support for a window manager. While reading the spec, I
noticed that it doesn't mention that programs with
_NET_WM_WINDOW_TYPE = _NET_WM_WINDOW_TYPE_DOCK cannot be moved, however, other
window managers and the dock programs themselves assume this. I could not find
any information in the EWMH or ICCC specification that specifies this behavior,
or that this behavior should be used for any other atoms with other dock-like
functionality (e.g., setting struts). I tested this with the dock program
"plank" and the window manager "awesome".

My questions then are:
* Is this an example of behavior that is part of a "de facto" standard for
  interactions between window managers and clients, that EWMH/ICCC are only
  subsets of? Or, have I simply misread the spec, and this behavior actually is
  specified in it somewhere?
* Is there a better resource for understanding how to correctly implement a
  window manager that supports these extensions than simply reading the source
  code of other window managers?

Many thanks,
- Ornxka