[cssom-view] Should browser zoom affect screen.width?

In Firefox and IE/Edge, the browser's zoom level affects screen.width (so that as you increase the zoom, the reported value of screen.width decreases). In Chrome and Safari, it does not.

The spec says:

The width attribute must return the width of the output device, in CSS pixels.

My reading of this is that, since it says "in CSS pixels", Firefox and IE/Edge's behaviour is correct (since zooming in decreases the number of CSS pixels that fit onto the screen).

Due to the implementation divergence, I'd like to double check: is this the intended interpretation?