This gets pretty deeply philosophical (see e.g. https://en.wikipedia.org/wiki/Indeterminacy_in_concurrent_computation), but as far as I can tell, he's saying that in the Actor Model, whenever an actor has multiple inputs, there's a magic box that decides the ordering of the incoming messages any way it wants to, even if it means delaying some of the messages for an arbitrarily long (but bounded) time. I.e., you can never rely on any particular order or time for receiving parallel messages, even if the program structure seems to favour a certain arrival order. (Note that this is a theoretical concept for reasoning about actor programs - you wouldn't try to make a system unnecessarily random in practice, except for testing purposes.)
The semantics of Erlang message passing say pretty much the same thing: whenever two processes send a message each to a third process, and there is no ordering constraint on the individual send events, you can never rely on which message will end up first in the receiver's mailbox. They could be arbitrarily delayed, even if all processes run within the same Erlang VM. Again, this is about what guarantees you get as a programmer (none), not about making the Erlang VM insert random delays. (Random delays can be introduced naturally by other things, such as OS-level pauses for page faults.)
