The NEC requires listing. For example, see sections 358.6 for EMT, 344.6 for RMC, 348.6 for FMC, etc., as well as 300.15 ("Fittings and connectors shall be used only with the specific wiring methods for which they are designed and listed.")
With that said, neither your complaint nor the practice is unheard of, but whether or not it's accepted is up to the AHJ.
