When something is printed as 100% black and set to overprint, the output will be pure black. No registration issue as the 100% element is carried through the other color breakouts. However, in AI CC 2019m when I zoom way in on text which is 100% black and overprinting, I can actually see through the black type. The intensity of the black varies based on what is underneath. One can even watch the black become muted in appearance as one zooms.

Shouldn't 100% black appear as 100% black regardless of being set to overprint or not.