While I completely agree with your point that there are things that are better shown then described, it doesn't seem that difficult to say, "The home button is positioned such that it is too easy to accidentally hit it."
Currently the only way to influence it is to delete registry key
[-HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\SurfaceHomeButton]
and kill all physical buttons completely.
A) The product hasn't even shipped yet. That may be an option or made into one in an early update.
B) There may be a technical limitation to disabling or rebinding it (e.g. without impacting either other buttons, or the behavior of actual keyboard buttons).