Sorry, I should have been more specific when I said "headless" because there are a couple of different interpretations:

- Headless software (can run without a GUI): https://en.wikipedia.org/wiki/Headless_software

- Headless computer (can run without a monitory nor input devices): https://en.wikipedia.org/wiki/Headless_computer

macOS has VNC built in so it can run as a "headless computer" but you cannot run it without the GUI. So you end up paying a massive memory and disk storage tax for running any CLI tools.