I remember a thread from way back where someone shared an experience of a vendor at an audio convention that deliberately reversed the speaker input connection?
More than likely one of the components in the amplification chain inverted phase, therefore, the vendor was merely attempting to re-establish correct phase. As previously noted, there is not a recording standard for phase, therefore, source material is all over the map with respect to phase. You have a 50/50 chance of getting it correct.