To be fair, this is just how executable scripts work — it’s not a special yaml shebang, just a regular shebang for an executable that happens to take yaml files

To be fair, this is just how executable scripts work — it’s not a special yaml shebang, just a regular shebang for an executable that happens to take yaml files as it’s input. The underlying OS just invokes the command in the shebang and passes the file as the first parameter, exactly as it would if the shebang were for bash or python.