I have a hard time processing… 
If i summarize:
- updating the grub package doesn’t actually update the binary in MBR/UEFI; so unless manually reinstalled, the version used there is the one put when the system was installed
- a flag added upstream has been reverted in the latest Manjaro’s build, in order to keep backwards hardware compatibility
- in the case of an installation using LUKS full disk encryption, the above change causes the present issue
- in order to fix that issue, one must manually add the cryptodisk module and push grub into the MBR/UEFI
Did i get that right?
Also, can the fix be applied before rebooting in order to prevent the issue?