One of Nikon Zf‘s benefits is the ability to shoot monochrome with the turn of one little dial. NEF (e.g. RAW) files are captured in color, and the JPEGs are strictly black and white.
While a convenient contrivance, the feature is an imitation of what Leica Q2 Monochrom, or its successor, can do. By removing the encumbrance of the RGB-color overlay, Leica delivers a camera that shoots photos with superior IQ (image quality), relatively little noise in low-light, and rich tones and dynamic range—all editable in the actual RAW file.