That IS absolutely hilarious.
And admittedly, it's quite clever. He doesn't really have to do much other than sign in, just stand there and watch the chaos unfold.
I don't understand what's so clever here. Even the article states:
"Granted, most likely won't fall for this trick, and if they do, there's no guarantee they'll actually sign out. Maybe the Xbox won't catch it, or they won't click through and finish the sign-out."
The Xbox doesn't just turn off, it also gives an "are you sure?" prompt that you can simply say "no" if one was dumb enough to fall for this. So really, it's literally impossible to "accidentally" turn off your machine even in a fit of rage directed at someone else.