I don't think it's fake but it's the lack of partition being the main
issue.
I've just reconnected it to the previous system and found this in history:
sudo mkfs.exfat /dev/nvme0n1
sudo mkdir /mnt/nvme0n1
sudo mount /dev/nvme0n1 /mnt/nvme0n1
I think the fact that it reported as nvme0n1 cofused me and made me
think it was a partition.
All of the above worked and I was using the drive for days.
I ran: rsync, ls, df, cd, rm, rmdir and other commands.
Everything felt perfectly normal.
Now I'm unable to remount it the same way:
sudo mount /dev/nvme0n1 /mnt/nvme0n1
mount: /mnt/nvme0n1: wrong fs type, bad option, bad superblock on /dev/
nvme0n1, missing codepage or helper program, or other error.
I think it's time to give up on the data and move on...