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."
I'm sure they did draw on it. But, there's a difference between drawing to make sure drawing works and drawing because that's your job. In the first, people would be more likely to say "oh I brushed the home button". In the second, they're much more likely to suffer a critical flow interruption.
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).
