Hmm, needs more investigation. You can move out the /etc/grub.d/25_bli file from /etc/grub.d folder on your system: GNU GRUB Manual 2.12: bli
You may also want to add the following to your /etc/pacman.conf
NoExtract = etc/grub.d/25_bli
Pacman: Skip files from being installed to System
Then update grub.cfg via update-grub and double-check if the BLI section got removed.
Issue I found in the Arch Forum: