That image is probably old residue, if you use use the microcode hook now. In any case your /boot mount will be the same as /efi.I do still have a /boot under my root file-system but the only thing that resides there is "amd-ucode.img"
Good catch. @Anluz you need to use the existing efi partition, two on the same device are not supported by UEFI. Grub will add itself in subdirectories there.Also it seems like you are dual-booting since you also have an two efi
Best you explain how you wanted to create the /boot partition (separate, within /, or within /efi). The mounts before and grub-install after must take consideration of that.

