man e2label wrote:e2label - Change the label on an ext2/ext3/ext4 filesystem
...
It is also possible to set the volume label using the -L option of tune2fs(8).
Label is part of filesystem's metadata. It is stored
in the disk.
UUID is also part of filesystem's metadata.
You can see both with
lsblk -f
You are right that the /dev/{[hsv]d,nvme}* names are not persistenly and predictably enumerated and assigned.
When you add label, you can refer to this specific (filesystem in) USB drive no matter what /dev/sd* it gets.
However, if you have two filesystems with identical label, then you can't differentiate between them with the label.
(I had RAID mirror; both disks had identical copy. Then something broke and system could not enable the mirror; writes went to one and that too changed on reboot.)
That should not be a problem for you; you connect at most one USB drive at any given time.
Similarly, if you had a rule to call every USB drive /dev/johndoe, how would it name two simultaneously connected drives?