Agreed for the most part - but are modern-day marketers not aware that there are more tools at their disposal? As a marketing professional, about 90% of what is described as growth hacking is, in my opinion, just plain old marketing. And most of it is pretty understood in my circles - content marketing, SEO, SEM, landing page optimization, etc.

There is a product part of it as well - so my conclusion is that growth hacking is probably more about a different way to think about product management than marketing. The examples given of Hotmail and others fall into that bucket - making changes to the product itself to drive growth.