I have a CMYK PDF I exported from InDesign CC 2015.
When I Preview Separations in InDesign CC 2015, black text correctly show up *only* on the black plate.
But not when I Preview Separations in Output Preview using the default US WebCoated (SWOP) v2 under Acrobat DC Pro 2015?
This should NOT happen, only the appearance of color should change -- not it's underlying Device CMYK values.
Curiously, when I select the same CMYK ICC profile assigned to the original InDesign document, in the Simulation Profile menu, all of a sudden, black text only show up on the black plate.
I can't explain this behavior.
As a "mental sanity check", I can rasterize the exported PDF in CMYK in Photoshop CC 2015 and, surely enough, black text only shows up on the black channel.
True story.