Indeed the generated /var/lib/dpkg/info/lvm2.postinst does not start lvm2-lvmetad.socket at all, even though debian/rules calls
dh_systemd_start --restart-after-upgrade \ lvm2-lvmetad.service \ lvm2-lvmpolld.service dh_systemd_start --no-restart-on-upgrade \ lvm2-lvmetad.socket \ lvm2-lvmpolld.socket
So this could be a bug in dh_systemd_start that misinterprets the --restart arguments, or a more subtle thing -- running the build with DH_VERBOSE=1 should get an insight.
Indeed the generated /var/lib/ dpkg/info/ lvm2.postinst does not start lvm2-lvmetad.socket at all, even though debian/rules calls
dh_systemd_start --restart- after-upgrade \ service \ service on-upgrade \ socket \ socket
lvm2-lvmetad.
lvm2-lvmpolld.
dh_systemd_start --no-restart-
lvm2-lvmetad.
lvm2-lvmpolld.
So this could be a bug in dh_systemd_start that misinterprets the --restart arguments, or a more subtle thing -- running the build with DH_VERBOSE=1 should get an insight.