Depois de muita pesquisa, acho que uma combinação desses dois links foi onde eu encontrei a frase:
Mestrado pela primeira vez: DnD
Also, don't name monsters, describe them. The players shouldn't know
that they're up against goblins, but that they're up against short,
green humanoids with pointy ears, shortbows and short, curved swords.
Sure, one of them might know from a knowledge roll that it's a goblin,
at which point tell them, but always start with descriptions.
Um guia para o DM preguiçoso
Don't name monsters
ehrin
Remember it's your world: thus, skeletons can have 80 hitpoints if
they need them. your monsters don't have to be exact matches for the
monster manual, they just need to be monsters.
Don't tell them the answers: my guys fought 'creatures' that i
described. they invented their own names for them, and never knew that
it was really a ghoul, or a goblin, or a gnoll. Don't say “you see 10
orcs on a hill”, tell them "you see ten creatures, loud, arguing,
boorish. They have a pigs face on a stout body…. etc.". If you never
admit to it being an Orc, then they can't holler how many hitpoints it
had, etc. and that it should have fallen, or can't be immune to sleep,
etc.
O último é de uma cópia de um tópico arquivado no antigo Fóruns de assistentes de 2007 .
Pode haver uma fonte mais primária do que isso, ou do Dungeon Crawl Classics, de acordo com a outra resposta, mas até que alguém publique isso, aceitarei a resposta do DCC, pois isso oferece muito mais contexto.