Well we just never know who wrote those narratives as they are not updated over time I would suspect. By todays power hungry homes it may be “low” but still doesn’t mean it is not compliant and adequate for the home you are inspecting.
The problem that any HI’s struggle with is that they are allowing their eyes to take the place of a calculation, a calculation mind you that they are not required to do or perform so it makes it very hard for the HI. My golden rule is always report what you see and never assume what you do not see.
Take your 600 sq. ft unit and lets do some dwelling unit (single) math with just some random values.
600 sq. ft x 3 VA = 1,800 VA
(2) SMBC @ 1,500 VA each = 3,000 VA
(1) Laundry Ckt @ 1,200 VA each = 1,500 VA
(1) Typical Range @ 8KW(KVA) = 8,000 VA
(1) AC vs. Heat (largest) @ 5,000 VA
(1) Microwave (at best) at 1,200 VA
Now for kicks and giggles lets just use the Optional Method for this dwelling unit.
General Lighting & Receptacle Loads Step 1 - 1,800 VA (General Lighting & Receptacle) + 3,000 (SABC) + 1,500 (laundry) for a total of 6,300 VA.
Appliances Loads Step 2 - 8,000 VA (Range) + 1,200 VA (Microwave) = 9,200 VA
Apply the Demands in 220.82(B) - 15,500 VA (combined step 1 and 2) -10,000 = 5,500 VA. So the first 10,000 VA at 100%, which is 10,000 VA and the remainder at 40%, the remainder was 5,500 x 40% = 2,200 VA.
So 10,000 VA + 2,200 VA = 12,200 VA
Heating or Air Conditioning [220.82©] - In our case we compared the heat to the AC and the larger of the two was 5,000 VA so that is what is used.
Now it is 12,200 VA + 5,000 VA = 17,200 VA, the Demand Load.
17,200 VA / 240V = 71.66 Amps which takes to a need for a 100A Feeder or Service.
So again what may look small may be rather adequate. Interesting note, based on diversity I was at a house, rather large house the other day helping a friend who had some electrical issues and we turned on nearly everything in the house, all that we could anyway and clamped an amp meter on the service conductor (each leg tested) and the maximum draw was 52 amps in his panel. Yes, it is Texas and his AC was on and range was on and all lights on and so on…best we could do.