fast answer: no you don't,
full answer: from what i know zfs (the filesystem of truenas, underlying os of HexOS) have different stage of speed:
under 80% the storage is fast en responsive, this is the base mode: the performance mode
over 80% the file system is going from a performance mode to a more slow mode (zfs is attentively looking for freespace on disk to store files)
so after you hit the 80% trigger the warning is on and you shouldn't ignore it it you are really near the full capacity (99%+)