Not strictly a bug, but certainly weird.
I changed my cache pool to ZFS, and redownloaded all docker containers.
I did not do any snapshots, but ZFS master reported that I have hundreds of snapshots and it shows each of the image file as a snapshot. I use directory for docker images.
Is this an expected behavior? Also please note that since each docker image counts as a snapshot, it takes ~10 seconds to load the main page. Granted, if I use docker.img or don't use ZFS master it will be less of a problem, but still weird.