Help me settle an HVAC argument

HVAC engineer, 8 years of experience in consulting. Recently moved into construction. I have been arguing with my manager (who is very much a construction guy, not a consultant) that we cannot install a CAV air handling unit on a system with VAVs and expect it to work correctly. He flat out refuses to listen to me. Myself and HIS boss insist that the AHU needs to be equipped with a VFD to compensate for the operation of the VAVs, he is insistent that this is not the case and that we can still operate a CAV system with VAVs. Can I get a sanity check here? Am I being gaslit by my manager or have I somehow spent my entire career misunderstanding how AHUs work?