Actually, thinking about this twice, I think you made a wrong assumption here. "-display" is about the GUI backend that should be used. "-M" is about the emulated hardware. The emulated hardware options should never influence the host backend options. And it is e.g. perfectly valid to use the "none" machine as CPU instruction simulator in a GTK window, so it does not make sense to force the disablement the GUI in that case.
** Changed in: qemu Status: New => Invalid -- You received this bug notification because you are a member of qemu- devel-ml, which is subscribed to QEMU. https://bugs.launchpad.net/bugs/1884507 Title: 'none' machine should use 'none' display option Status in QEMU: Invalid Bug description: As the 'none' machine doesn't have any peripheral (except CPU cores) it is pointless to start a display. '-M none' should imply '-display none'. To manage notifications about this bug go to: https://bugs.launchpad.net/qemu/+bug/1884507/+subscriptions