Part of the problem is that "neutral" means different things to different people. To some, it resembles the Harman curve; to others, the diffuse field target; to others still, "what the HD 600 sounds like".
Other than the elevated treble and deeper bass extension, the HD 560S does closely resemble the HD 600 in frequency response.
Yep yep. There does seem to be some general consensus about the excess HF energy though, and I think it could make judging mix decisions around sibilance, hi hat EQ etc more difficult than a "more neutral" headphone.