Your findings are completely normal for a physical disk like an Apple SSD.
A common physical disk partitioned in macOS doesn't contain (a) file system(s) but a partition table, partitions and some unallocated disk space on the first layer.
Consequently it can't be mounted and has no volume name/file system.
On the next layer (disk0sX) a partition usually is formatted with a file system and has a volume name (e.g. disk0s1: FAT32/EFI disk0s2: HFS+/"Macintosh HD").
In newer systems - especially with SSDs - another layer is added: an LVM (CoreStorage) and disk0s2 as a physical volume is part of an Logical Volume Group (which can contain one or more of them). Almost the entire part of an LVG (i.e. a logical volume) is formatted with a file system and mounted with a volume name as a new logical disk (usually disk1 in a system with one disk or disk2 in a system with two disks like a Fusion Drive). Small parts of an LVG are not formatted with a common file system but contain administrative data (usually less than 0.3% of the total size of an LVG).