3.197~ppa17 update:
i suspect that the fact that some BIOS still boot the Windows efi file (not grubx64.efi) after installing grub-efi is due to the fact that grub-efi is installed from a Legacy session. So i made the following change in the PPA:
- when B-R reinstalls grub-efi from a UEFI session, the "Backup and rename EFI files" option will be deactivated by default
- when B-R reinstalls grub-efi from a Legacy session, it will display a warning saying "Your BIOS is in Legacy mode. You may want to retry after changing it to EFI mode. DO you want to continue?", and by default the "Backup and rename EFI files" option will be activated (except if some .bkp files are detected, as described few posts ago).

Please warn me if some UEFI computers still boot directly Windows (without showing GRUB) after running the Recommended Repair.