It was often mentioned. Like when Wray took over and assigned Airmen instead of "his Marines" to a gate mission. Also except when the Lieutenant was being snarky he was never addressed as Master Sergeant as a Marine NCO would be. I have speculated that because of the actor's young age the character may have started out as an USAF Master Sergeant before they made him an USMC Master Sergeant
The Air Force officers calling him Sergeant I can let slide due to Air Force officers not being used to Marine Corps customs. Greer letting them do it is what's out of place. Any self respecting devil dog NCO will respectfully correct someone of a higher rank and dress down anyone below them for the mistake.
The thing is, even in the Air Force it's still a terrible breach of etiquette to call someone with the Master Sergeant, Senior Master Sergeant, or Chief Master Sergeant ranks simply "Sergeant". So, even AF officers should know better.
If they REALLY wanted to be "accurate" (with regards to how things work in the real world, as per customs and tradition), they should have had the people closest to him call him "Top".