No one makes sergeant within days of joining the army; especially in the peace time army. In the time before the war it could take years to make PFC.
New recruits with only a few days in the Army are shown getting specialized training with weapons and equipment. In fact recruits go through six weeks or more of basic training to increase their fitness, coordination, and the very basics of drill.
This film would have you believe that within a few days recruits have learned all you need to know to function as a soldier.
A drill Sergeant would never salute any officer who was in civilian clothes. And it's completely inappropriate for an officer to return a formal salute when not in uniform.
The Presidio was never used a basic training center. It was used for some advanced training during World War II. Many units have been headquartered there.
Sgt's do not eat at the same table as trainee's. There are lines drawn between NCO's and privates & PFC's.