I have never measured a zero v-drop atty. I have heard of them but I find it difficult to believe, physics doesnt support it.
Resistance in the circuit, no matter where it comes from, will consume some energy. If the energy isnt converted to usable heat then it is wasted for our purposes. All metals have some resistance at normal room temperature in normal atmosphere, even your no-resistance wire.
Standard atty resistance meters dont measure accurately enough to see what we are talking about here.
Your atty may have an very very low voltage drop, but it does have one, you just might need special test equipment to measure it.
I "suspect" your answer has more to do with their definition of "zero voltage drop".