a common Class-D complaint, as they have output filters to rid the switching noise that create phase shifts down to 3-5khz.Probably true of a subwoofer amp, but not any that are meant to run full range.
Typical filters on a class D are 12db; if an 80KHz filter, this limits phase shift to well above the audio passband; of course dependent of the Q of the filter! Essentially though the statement quoted above is false.