They effectively do. All css absolute units are effectively defined as ratios of each other and zoom*DPI*physicalPixels sets the ratio of how many physical pixels each absolute unit will end up turning into. Increase zoom and the screen seems to have shrunk to some smaller 'cm' and so on.

For things like 'vh' and 'vw' it just doesn't matter "how many cm" the screen is as 20% of the viewing space always comes out to 20% of the viewing space regardless how many 'cm' that is said to be equivalent to.

Oh duh, right. Thanks!