True and false...
From what I understand, Neve discovered that one of the transformers in the chain wasn't terminated properly, and as such was creating a "ringing" spike around 56K
However, anyone who's looked at a tone on an FFT plot will know that - unfiltered - you will observe overtones at various divisions, i.e. in the case of 56k: 112k, 28k, 14k and so on...
Therefore, to my knowledge, it is generally accepted that Emerick picked up on the overtones that were within the 20k range.
Justin