I just verified on x86 + 14.04, and it looks like any changes to the GRUB_CMDLINE_LINUX_DEFAULT do not end up making their way into /boot/grub/grub.cfg.
It turns out /etc/default/grub.d/50-curtin-settings.cfg
sets GRUB_CMDLINE_LINUX_DEFAULT=""
I'm not exactly sure why this is, but I'll move this case over to curtin as it seems to be the culprit.
I just verified on x86 + 14.04, and it looks like any changes to the GRUB_CMDLINE_ LINUX_DEFAULT do not end up making their way into /boot/grub/ grub.cfg.
It turns out /etc/default/ grub.d/ 50-curtin- settings. cfg LINUX_DEFAULT= ""
sets GRUB_CMDLINE_
I'm not exactly sure why this is, but I'll move this case over to curtin as it seems to be the culprit.