SEOs should be a laser focused thing, but it is more likely a catch all title for "internet marketers" and the industry seems to be fairly good at latching on to any buzzword in the online marketing world. SEOs last big bandwagon was social media gurus, especially on twitter. Now Growth Hackers? Um... yay... :(
I secondly hate on social media "gurus" as well as SEOers who can't code (or at least read html).
IMHO: Growth Hacking is just Inbound Marketing for startups. Going from 0 users to 1MM+. You leverage all the online marketing skills: seo, ppc, email, display (retargeting), ux, social, cro, etc.
BTW, nice post John - glad to see it on here as well as inbound.