Perceived differences between the two practices will certainly emerge from these data. But what is it? Well, for what it's worth, my take involves the coordinated evolution of the term (perhaps some underemphasis) by HubSpot as it expands its product suite. In short, with

HubSpot launching everything from campaign management, Salesforce automation, help desk applications, content management and industry mailing list service, HubSpot is no longer just a tool to help generate leads at the top of the funnel. It is a complete CRM suite that competes with many other enterprise marketing clouds.

It only makes sense that their definition of inbound will evolve and be broader. Inbound marketing has evolved from the original description in HubSpot's seminal 2009 book of the same name by Brian Halligan and Dharmesh Shaw.