Came here as well after installing a new TrueNAS Scale machine with 12 HDDs and 2 SSD's in
2x HDD Raid-Z vdev á 6 drives and the 2 SSD's used as a metadata mirror.
Glad to see it's still "OK". Our server is only used to pull backups from another server which is running raid-z3 so since this is the "datacenter burned down"-recovery server it's fine.
But a more explanatory info message would be good, even though I always enjoy going to the forums to realize I can never learn enough about TrueNAS / ZFS.