Authentication, authorization, and resource quotas for agents are not really addressed in the Erlang model, but would be expected for IPC on a Unix-like system.
Do we really want to put all of that into the kernel and not implementing it in userland? I get the feeling that it's too much application dependent, not enough general principles.
Maybe I just don't understand the problem they are out to solve.
The reason for a bus-style IPC implemented in the kernel is the same that sendfile(2) exists. I doubt anyone thinks it's the pinnacle of great design, but reduced copies and context switching for real application workload: sometimes the more 'proper' design is sacrificed for practicality.
Maybe I just don't understand the problem they are out to solve.