systemd-fsck at .service

[Tom H]

I have two questions about systemd-fsck at .service.

1) How does the unit now what "%f" is?

$ grep -Ev '^#|^$' /lib/systemd/system/systemd-fsck at .service
[Unit]
Description=File System Check on %f
Documentation=man:systemd-fsck at .service(8)
DefaultDependencies=no
BindsTo=%i.device
Wants=systemd-fsckd.socket
After=%i.device systemd-fsck-root.service local-fs-pre.target
systemd-fsckd.socket
Before=shutdown.target
[Service]
Type=oneshot
RemainAfterExit=yes
ExecStart=/lib/systemd/systemd-fsck %f
TimeoutSec=0
$

2) "%i" is, in the case that I set up a few weeks ago,
"sys-devices-pci0000:00-0000:00:0d.0-ata4-host3-target3:0:0-3:0:0:0-block-sdb-sdb1".
Should it have "sdb" in it since it's supposed to be an unstable name?

It corresponds to
"/sys/devices/pci0000:00/0000:00:0d.0/ata4/host3/target3:0:0/3:0:0:0/block/sdb/sdb1",
which, I think, udev calls DEVPATH.

Shouldn't it be using a udev property, like by-id/by-path/by-uuid,
that doesn't include sdX?