They must have changed their CMYC to RGB conversion algorithm as well. CMYC colors now look different in Preview compared to when rendered in Acrobat Reader or using Ghostscript
I'm guessing that the rendering is actually more accurate in Preview, not that it helps. Reader has an awful habit of displaying all blacks in CMYK documents as composite, which has bitten me occasionally when going to print…
They don't think it's a bug, as it was marked "as intended" or something.
But I'd disagree. No Adobe software does this by default. Trying to simulate a reflective medium in a emissive one by decreasing the latitude can be useful at times, but simply showing it like that with no option to turn it off seems crazy to me.
I've had this complain (and bug filled) for a long time. They changed it a few years ago, blacks are completely washed out.
But I haven't yet had the inclination to install Sierra.