Active Twitter User? Thoughts on Hubspot's Methodology

From the article: "An active user, as defined by HubSpot, may be a member 3 or 6 months old who has abandoned his account"

"What’s interesting are the population metrics stating that 44.5% follow 1 or more people and 47.29% have 1 or more follower. Firstly, they never took out “inactive users” (even according to there own erroneous definition)."