"Are you saying that someone with access to a cloud document can't email it out to a client? If so it's not much use to anyone."
No, that's not what he is saying. Think of Google Docs like a server, because that is exactly what it is. It is an app (word or spreadsheet app) that a bunch of users can log into an work on at the same time. You can share a Doc by giving some other user access to it, as many as you want. When you share that doc or sheet or whatever, there is a log of who shared what with who, when they did it, etc. Full visibility. If the person who shared it or IT wants to revoke someone's access to that doc, they can do so at any time.
What he is saying is that is way different than MSFT Office where everyone has a million files on their desktop and IT or security has no idea what they have or what they are doing with it.
Think about the scenario when a person leaves your company, maybe to go work for a competitor. You can revoke access to online services, like email and corp services, almost immediately. If that user is at home with their laptop though, they can pull whatever they want off their PC and, provided they go offline and do not come back on, you can't stop them or even see that it happened. With Google G Suite, productivity apps just become like SAP or email or any other corporate service, you revoke access, people can't access docs, sheets, etc.
Think of how crazy it would be if I said we are going to have every user download a local copy of the CRM database to their personal PC. People would go nuts. One PC gets compromised and the entire database is exposed. One bad employee can hand off that DB to whoever. Yet that is the crazy world that most people live in with MS Office... where all kinds of employees have huge Excel sheets with the equivialant of a CRM database on them.