"At Y Combinator, we advise most startups to begin by seeking out some core group of early adopters and then engaging with individual users to convince them to sign up." Sounds like marketing and user acquisition to me...
I think the article's message is same as "Do things that don't scale". Marketing is something used to get users in large volumes (certain groups) vs sales is more of a one-on-one approach. Once you have figured out what works in these one-on-one sessions, you take that message and scale it up as your marketing message.