NPCs like this one in Ashenvale spawn a chest upon death that gets tracked + recorded by this addon:
https://classic.wowhead.com/npc=3928/rotting-slime

The chest is this one:
https://classic.wowhead.com/object=19021/rusty-chest

Since they are not spawning in fixed locations, only a certain area (and only spawn on the spot the NPC dies), the location of these chests should not be recorded by this addon.

There is no way to determine if the "chest" in this case would be a world drop or not.

my guess is that they dont track anything but rather add them manually.

I wonder how websites like Wowhead track the location of these nodes?

in that case i would need a database of all the "chests" wich it shouldnt record on all languages.

GatherLite at least definitely does know the name of the container, right? Could there be a blacklist of container names that are not being recorded or dropped from the database at least?

I also got the harvest festival items as "treasure" node in my database now. I'd be more than willing to help with creating such an ignore/purge list. In general I think wowhead already has a lot of this data, so just knowing the english name should already be enough to compile this list:

https://fr.classic.wowhead.com/object=19021/coffre-rouill%C3%A9
https://de.classic.wowhead.com/object=19021/rostige-truhe
https://es.classic.wowhead.com/object=19021/cofre-oxidado
etc. (e.g. try ru.classic.wowhead.com with the same object id)