Sure enough the LVM subsystem could make things better for one to notit shouldn't need all of the PVs you just need all the pv where the
need all of the PVs in the root-containing VG in order to be able to
mount root read-write, or at all, but if you think about it, if initrd
is set up such that you only bring up the devices that hold the actualin this case just regenerate the initramfs after modifying the vg that
root device within the VG and then you change that, say by taking a
snapshot of root, moving it around, growing it, etc, you'd be better
off if you could still boot. So you do want all of the VG members to
be around, just in case.
Yes, this is an argument against root on LVM, but there are arguments
*for* root on LVM as well, and there's no reason to not support both
behaviors equally well and let people figure out what works best for
them.