UEFI still boots. Spec said it can boot from fat in an eltorito floppy image and sun disklabels sit in the second or so sector. Spec also said it abstracts the type of volume so all boot methods always work for all drives. ISO images don't use the first 4kB so it doesn't see there's disklabel at all

So now I can mount the ssd as iso9660 but there's also partitions on it of which the third spans the entire drive (of course, because that's the c partition)