No problem with the device drive. These are two different raspi 3 one with 12TB and the other one with 9TB Raid. 
[hr]
You have to replace %k with your partition. Just a guess, but perhaps the disk is not quite ready somehow at the time when udevil runs.
I tried the command on 1022 and 1023
/usr/bin/systemctl restart udevil-mount@/dev/sda2.service
On build 1022 it works fine on 1023 not. I made a sha1 checksum compare of the udev rules on both builds... no difference
Here the blkid Logs:
1022
/dev/mmcblk0p1: SEC_TYPE="msdos" UUID="176D-2AFE" TYPE="vfat" PARTUUID="99176dab-01"
/dev/mmcblk0p2: UUID="f2c26989-d7ab-4c16-9d6a-36e40c02035b" TYPE="ext4" PARTUUID="99176dab-02"
/dev/loop0: TYPE="squashfs"
/dev/sda2: LABEL="RAID3" UUID="8CC8F603C8F5EB7A" TYPE="ntfs" PARTLABEL="Basic data partition" PARTUUID="df1b0053-a29b-483e-8550-4592ca85f9a8"
/dev/mmcblk0: PTUUID="99176dab" PTTYPE="dos"
/dev/sda1: PARTLABEL="Microsoft reserved partition" PARTUUID="f40f75aa-7f98-4d6e-9507-86e2944e7673"
1023
/dev/mmcblk0p1: SEC_TYPE="msdos" UUID="176D-2AFE" TYPE="vfat" PARTUUID="99176dab-01"
/dev/mmcblk0p2: UUID="f2c26989-d7ab-4c16-9d6a-36e40c02035b" TYPE="ext4" PARTUUID="99176dab-02"
/dev/loop0: TYPE="squashfs"
/dev/mmcblk0: PTUUID="99176dab" PTTYPE="dos"
/dev/sda1: PARTLABEL="Microsoft reserved partition" PARTUUID="f40f75aa-7f98-4d6e-9507-86e2944e7673"
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On 1023 the sda2 partition gets not recognized.
Greetings.