If anyone with more than six months experience submitted that vehicle PR with a half dozen interfaces we'd be having a chat outside of the review because that's pretty bad. That might be the worst code in the entire article, and it's supposed to be one of the good examples? This is even ignoring the fact that there are languages that don't support multiple interface inheritance which isn't that big of a deal but hints that the author may not have a ton of experience outside the couple languages he works in every day.