Status: OUT
Counter's zero-default for missing keys and sentinel initialization for loop state are not independent convenience features but structurally coupled components of the streaming paradigm: both encode boundary conditions into initial state so that the streaming loop body requires no special-case logic — well-chosen defaults are the mechanism that makes streaming self-sufficient rather than requiring explicit setup.
Streaming's claim to require no preprocessing depends on defaults silently handling boundary conditions; defaults are the hidden infrastructure of streaming's zero-prerequisite property
Depends on (SL): defaults-encode-domain-knowledge-at-every-layer, streaming-is-self-sufficient-paradigm