Are you refering to the CMYK image input profile? OnyxCMYK is definately not accurate and does not have a typical cyan bias. It is however capable of making a pretty picture when paired with the Default Printer Icc provided by Onyx. Typically not accurate considering most provided data will be either SWOP or Sheetfed but perhaps good enough for some.
At any rate, in Onyx 7, this profile is no longer the default. They have switched to “US Web Coated (SWOP) v2.icc”. There may have been licensing issues with Adobe in the past. I’m not sure. I know the Adobe profiles are not provided in versions prior to 7.
I would import them and set up a custom Color Management setting. Change it to match your application settings and see what you think.