Just to clarify there is a bug in the plugin in that you have never gone into Settings->Disk Settings and hit Apply from that screen then there is no value set for at the UnRaid level for the Disk Warning temperature value and this results in the plugin thinking it is 0C rather than the default of 45C. A workaround is to ensure that you have set a value, but the next update to the plugin will handle this setting being missing and will then apply the default of 45C.
I suspect in practice most users HAVE set something via Settings->Disk Settings for some reason or other and as a result not encountered this bug.