It seems the OP is interpreting Bezos mandate as if he were talking about the interaction/communication between actual teams (people) as opposed to between each teams software service(s). Whereas there are parallels between these, I'm pretty sure Bezos wasn't saying anything about inter-team communication. It sounds like they already had a good company organizational structure but there were no limits on how services used each other, which would result in tight, often-hidden coupling that would be too complex to manage.
My guess is this was the thinking behind the mandate, limiting all inter-service coupling to a single, well-documented interface prevents the whole system from devolving into a big ball of mud; primarily because it forces all dependencies to be explicitly declared and documented in the same way.
My guess is this was the thinking behind the mandate, limiting all inter-service coupling to a single, well-documented interface prevents the whole system from devolving into a big ball of mud; primarily because it forces all dependencies to be explicitly declared and documented in the same way.