it’s canon! there are quite a few stories where it’s demonstrated in the modern comics, but it’s been a thing since the early days- like when Gladstone is determined to find a square-trunked speckled elephant for Scrooge (which he set a 1 billion reward for and doesn’t actually want)

and here where he identifies an ‘unlucky’ charm Donald owns

Gladstone wat u doin in haunted houses anyway oh and there’s this

y’know, just your average everyday knowledge there