They’re a rogue, what are the chances they haven’t done something to deserve it?

Silly bards. Barbarians can easily use instruments as adventuring “tools”.

They have much room in the forest to explore

For the uninitiated

That site is so annoying because it’s all homebrew/third party but gives the impression it’s official content.

Maybe they’re thinking of witch sight.

Witch Sight

Source: Player’s Handbook

Prerequisite: 15th level

You can see the true form of any shapechanger or creature concealed by illusion or transmutation magic while the creature is within 30 feet of you and within line of sight.

Or more likely, it’s a DnD meme, they probably didn’t read the description.