"Where does it state in the code I cannot use breaker in MCC bucket w/out thermal protection/starter?"
240.4 states that you must have over-current protection for all conductors, then goes on to say that motor circuits are covered under article 430.
430.52.C.3 then states that Instantaneous trip circuit breakers can only be used as part of a listed combination motor controller assembly that includes an over-current device (overload relay). If you use the MCP breaker all by itself, it is no longer part of that listed assembly.
Don't get me wrong, this has only to do with MAG-ONLY breakers, commonly referred to as MCPs or Motor Circuit Protectors. Standard Thermal-Magnetic circuit breakers are fine as stand alone feeders.
