Trying to copy EFI into a partition, without any success

Hello guys,

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I'm following this guide How to install macOS Big Sur , but I get stuck when I have to copy the EFI folder into the partition, because I'm not allowed to copy it.

NOTE: I'm not used an external USB, but an external mini HDD (shouldn't be the same thing?)

https://preview.redd.it/ifqyussi8oq71.png?width=1276&format=png&auto=webp&s=fcd4b6e68318f8e53cb59f6b68895fc523c536b3

https://preview.redd.it/wy5580l38oq71.png?width=984&format=png&auto=webp&s=eecfad4f1e3d05c4e0f27bfaff40500d7657512c

https://preview.redd.it/h1ovm4e58oq71.png?width=1398&format=png&auto=webp&s=4f1cda0ee128633ed7fb7c0dfa31255d50775bb1

Any idea why I'm not able to copy the EFI?