Booting in BIOS mode on a UEFI system with a GPT-formatted disk will also show a "protection layer".
Specifically “protection layer” is pretty vague, I’ve gone back to it because I wasn’t sure what to put instead. I might have encountered it once when I was a total newbie at installing a Linux system but cannot remember what was that protection layer (an error of sorts ?..).
My translation currently reads “couche de protection” which is the direct translation to “protection layer”… it feels awkward though as French here requires some detail.