Thank you for following up. This is matching my observation, that even if a disk is configured for HDD Standby (where Truenas used to stop temperature monitoring), temperatures are still listed in the reporting tab.
smartmontools shouldn’t be the reason in my point if view, since /etc/smartd.conf already contains -n standby, which should apply to all disks.
@AndBu could you please double check whether keeping smartmontools running makes any difference? For me, disk keep spun down without needing to change anything w.r.t. smart.
I have reported a bug w.r.t. this issue here: Jira