As far as I know those labels are not tied to any filesystem, nor
dependent on any. If you use i.e. Partition Magic you will find the
possibility to set a label, so does the old fdisk on DOS.
The Linux kernel requires BSD disk label support compiled in
(CONFIG_BSD_DISKLABEL=y) to use the labels with fstab and how it is used
as kernel command line in the grub.conf on Fedora (Redhat) systems.
While I think what you're saying is true (I don't use labeling at the
partition level) the labels that e2labl displays and modifies are
indeed an ext2/3 thing and apply to the filesystem, not the partition.
Devlabel, which I have not messed with, can supposedly be used to
label devices in a filesyste-independant manner by associating a
symlink with the device's UUID (see 'man devlabel' for more).
--Brad