Serpent Men polymorphic talents query

Would GMs here agree that the Conan npc Serpent Man (Kull p84) using sorcerous (Form of a Beast ) ‘polymorphic talents’ (Skelos p7 left) to disguise herself as human should not be able to attack with her Envenomed Bite?

My thinking is that this is sword & sorcery and was thinking about it’s rules of having to see it to hit it and if it bleeds…

If i remeber right from the Kull books, the serpent mens weren’t shapeshifting but rather using illusions to disguises themselves (and the scenery). Which would definitevely let them us their bite. And rules-wides shouldn’t use the Form of a Beast spell.