I agree, it was something I kept saying couldn't happen to myself as well. Yet 100% of the time when I shut down the service it worked, and 100% of the time I turned it on it failed.
I ran process monitor and I can confirmed your right, it does not ever specifically touch the files in C:\ProgramData\Docker\.
Further testing:
When I remove the SSD cache volume and with the drive pool service running; I can no longer reproduce the issue.
now the weird bit. My hypothesis was that the issue would return.
After re-adding the SSD cache volume to the drive pool with the drive pool service running. I am no longer able to replicate the issue,
I also tried rebooting and could no longer replicate the issue.