Before the 2 inches was in the code, AHJ's use a number of measurements to get the weep screed to have an air space. At one time in the code the weep screed was only used in conditioned space. So a unconditioned garage building would not have to have it. The weep screed is used more for keeping water out and off the building walls. Termite control would be the 8 inches needed from earth to wood seperation.
Termites will build their conduit and travel anywhere the want.
2304.11.2.8 Separate wood framing. [SPCB]
Correct the conditions in frame and stucco walls and similar appurtenant construction so that the wood framing is separate from the main structure by a complete concrete or masonry plug with no voids that will allow infestations to enter the structure from the wall. If there is no plug, the foundation shall be 2 inches (51 mm) or more above the grade levels and at least as high as the adjoining slabs or 4-inch (102 mm) concrete barrier seat off installed.
and IBC 2304.11.2.2 for other stuff.
The distance from grade to the exterior plaster screed is what forces this as a solution even though the curb isn't actually a "descriptive requirement" in the code, just as you thought. Note that the distance is 4-inches at landscape areas and 2-inches to hardscape [a concrete mow strip will qualify for this].
As designers of DSA-regulated projects, we always indicate curbs at these locations [and incidentally at every exterior building wall where the floor is at or close to grade]. This is to keep termites and other vermin out of the building as well as to reduce water "wicking" up the plaster or paper backing.
While in this instance the building department comment is sort-of vindicated by the code, I shudder to think that AHJs issue "corrections" without being sure they are actually needed.
Otherwise take a look at the conventional construction provisions in the code, there are metal framing requirements for light gauge steel.
2512.1.2 Weep screeds.
A minimum 0.019-inch (0.48 mm) (No. 26 galvanized sheet gage), corrosion-resistant weep screed with a minimum vertical attachment flange of 3½ inches (89 mm) shall be provided at or below the foundation plate line on exterior stud walls in accordance with ASTM C 926. The weep screed shall be placed a minimum of 4 inches (102 mm) above the earth or 2 inches (51 mm) above paved areas and be of a type that will allow trapped water to drain to the exterior of the building. The water-resistive barrier shall lap the attachment flange. The exterior lath shall cover and terminate on the attachment flange of the weep screed.