JoluMarti.9165:

New items don’t have an hint in their description.
https://api.guildwars2.com/v2/items/70862
{
“name”:“Invisible Mushroom Spore”,
“description”:“This item only has value as part of a collection.”,
“type”:“Trophy”,
level,
“rarity”:“Rare”,
vendor_value,
“game_types”:[“Wvw”,“Dungeon”,“Pve”],
“flags”:[“AccountBound”,“AccountBindOnUse”],
“restrictions”:[],
id,
“chat_link”:“[&AgHOFAEA]”,
“icon”:“https://render.guildwars2.com/file/02C8490298FE3913CDF15B30126275DBC8FD94F9/66919.png
}

Lawton Campbell.8517:

You’re gonna have to show me a screenshot — I don’t really know what you mean. The item doesn’t show a hint for me in-game.

Nightgunner.2896:

I think hints are part of the collection, not part of the item.

Mikuchan.7261:

I think hints are part of the collection, not part of the item.

The Tempest North Wind warhorn collection required Machined Warhorn twice instead of Tempest Loop, the armor piece. However the hint for the instance of Machined Warhorn that was instead of Tempest Loop had the correct hint for Tempest Loop while the real Machined Warhorn had the hint for the Machined Warhorn. (This is now fixed)

This very strongly suggests that the hint is indeed in the collection, as you say, and specifically that very space in the collection, as opposed to being tied to any item.