It's nonsense. A ZFS pool is created from block devices, and ZFS doesn't care if those are whole discs or partitions. Every ZFS pool I have is composed of GPT

It's nonsense. A ZFS pool is created from block devices, and ZFS doesn't care if those are whole discs or partitions. Every ZFS pool I have is composed of GPT partitions, and this is also recommended in ZFS books as good practice to make it easier to identify a failed drive. Since you see the GPT partition name in the "zpool status" and other tools' output, it's handy.