Yes, that is quite valid to say ... however, it's a very easy way to "measure" a system's competence by testing whether one can raise the volume without the sound appearing to falter. A simple one: find someone playing a real piano, competently, and move closer and further away to the instrument while it's being played, to within a few feet of it; try and retain a picture of how the sound impacts while doing this. Then, play a similar style piece of piano on one's system, up the volume to match being a certain distance from the real thing - does it reasonably match? You can try further experiments of increasing the volume to mimic getting closer, or in fact just physically move nearer to the speakers - does that match the "real thing"?
A complication is that the psychoacoustics of hearing can make playback come across, subjectively, as being softer or louder, without touching the volume control! The ear adjusts, depending on how comfortable it is taking in what it's receiving - which is why sound sometimes is very "big", yet is not measurably loud ...