Channels presented the notion of channels in the context of general nonmeta languages.
We (provisionally) stated that the fundamental channel types, such as chan(bool), were abstract in that they describe what information was communicated over a channel, but not how (encoding and protocol).
As far as the CHP level is concerned, the implementation is irrelevant (?) to the concurrent program semantics and functional behavior (and simulation).
Where does the implementation come into play? In automatic production-rule generation and mixed-level simuation involving production rule details.