24 bit guarantee nothing as itself. There are many mutually bound variables: band signal, sample rate, noise, bit-depth, analog and digital filters.
All these things give result in complex. Nyquist for audible 20 kHz is one of reference points, but it is not applicable rule for achieving of result.
I many times heard about Nyquist theorem without reference certain case to limitations of this theorem (infinite signal, that is not related to musical one, as example).
And real analog filters (about 48 dB per octave) don't allow to use Nyquist theorem (44 kHz sample rate here) for achieving of features, that we expect for hi-fi.