Hi Andy
It does look odd, but as Chris Murphy said the yellow can do strange things
within a CMYK grey balance.
I believe this GCR setting within the profile is causing the results you are
seeing, reducing the yellow in a RGB to CMYK conversion to reduce the
possibility of a yellow bias.
The grey balance for ISO for the CMY is:
Cyan Magenta Yellow
Quarter tone 25% 19% 19%
Mid tone 50% 40% 40%
Three qu. tone 75% 46% 46%
But this will not reflect the profile and any GCR that would be applied with
a RGB to CMYK conversion.
As you say the ISO profiles do work well, if the printers follow the
standard printing conditions associated with each profile.
Regards
Paul
The Missing Horse Consultancy Ltd
Telephone: 01442 871752
Mobile: 07899 906385