Atlassian could just as well title all of their engineers as "developers" and claim not to have an engineering team; the claim they're making is only true in a very narrow and ultimately meaningless sense.
They pay people to convince other companies to buy their product. The claim of "no sales people" stems from the fact that they only talk to people who contact them, rather than cold-calling.
This is, interestingly, also what the sales team at my company does. They are pretty sure they're doing sales, though, so we call them that.
[1] https://www.atlassian.com/licensing/purchase-licensing