GRUB_CMDLINE_LINUX="" should do the trick but won't work anymore
I suspect something is weird about the GRUB that ships with elementary OS. It ignored some of the configuration I tried on it as well, albeit I'm inexperienced with GRUB in general.
What worked for me was using
boot-repair to reinstall GRUB. I disabled Secure Boot in the GRUB options, which reinstalled GRUB, and enabled my selections in the GRUB config file.