Ask the inspector what national code they adhere to, and what local ammendments have been made. It's possible the local ammendments require the thermostatically controlled valve. I dont' think it is in any of the national codes. Local ammendments override the national ones. Ask him where you can read a copy and have him either show it to you or give you the reference so you can look it up. If it is just his preference, without it being adopted in local codes, he's blowing smoke.