You've confused by-label with the kernel's device nodes (e.g. /dev/sda1). Kernel names are assigned in order. Labels are just like UUIDs and part of the filesys

You've confused by-label with the kernel's device nodes (e.g. /dev/sda1). Kernel names are assigned in order. Labels are just like UUIDs and part of the filesystem. However, unlike UUIDs they don't necessarily exist, are not as likely to be unique (you should only get duplicate UUIDs by cloning filesystems) and are easier to change. This makes them less suitable for mount configuration.