It's Samsung, and the home doubling as power button is a Samsung feature. But you used to be able to remap it, until the Lollipop release. So not really Google's fault per se, but a continuing part of the trend to remove control and customization from users.
However, once a phone does get powered on and it's still in your pocket, then all sorts of problems will happen. There must be a way by law to dial an emergency number if if you can't unlock it (ie, you don't know the PIN or can't type it, say you pulled the phone out of someone's pocket who's having a seizure). Since everything is touch screen based now, just light jostling in the pocket is enough to make things start to happen. To emergency dial you just drag the phone symbol up about an inch, then typing a number is just basic tapping. When the phone was new you could also turn on the camera this way.
I never butt/pocket dialed with it, but it did happen on an older HTC phone that was more normal in how you turned it on. I got a call back from the 911 operators asking if I had a problem or not. Embarrassing.