With shaving related subjects interpretations differ and sometimes greatly. If everyone interpreted things the same way there would be a consensus, cut and dried, as to which soaps are good and which are bad, everyone would be using the same make/model blade, the same make/model razor and so on.
Without an agreed upon standard set of parameters it is subjective and varies person to person.
Anyone can do a one and done and get away with it as most people don't give a rats ass what your shave looks like. The only time anyone cared about what my shave looked like was during inspection in the Navy. Those days are long gone by 30 years.
So what are the parameters for a DFS? Things like is stubble not visually present when viewed from, say, 2-3 feet or absent from the touch when you check all over your face? How long should it last before stubble is detectable again?
Bob