For email that conversation probably has taken place already. Also, lots of larger orgs have internal mail servers where this isn't even remotely true.
They aren't talking about internal chat. The article suggests trying out several third party SaaS discussion forums like Discourse/Carrot/Basecamp. It's unlikely most orgs have internal servers for these services. GP is pointing out that using these third party SaaS discussions forums is usually a nonstarter unless its first been pre-approved by legal (whereas email is almost certainly already approved).
