That everyone on the Enterprise in TOS was an officer. Silly. Just damned silly and impractical.
I can buy GR's thinking on this. TOS was made in the era of the NASA astronaut-hero, the days of John Glenn and others. At that time, all NASA astronauts were college grads and all were officers.
GR wanted his TOS crew to be qualified astronauts, same as NASA, only in a future century. NASA only had officers as their astronauts, GR wanted no less. So okay, everyone on the Enterprise is an astronaut and an officer.