Botanist Jan Schlauer has noted differences between the type specimen of N. fusca and Sabah plants referred to this species, even interpreting plants illustrated in Kurata's Nepenthes of Mount Kinabalu as representing N. stenophylla (as distinct from N. fallax). Matthew Jebb does not consider these differences significant enough to merit distinction at the species level. He suggests that the type specimen consists of intermediate lower and upper pitchers as opposed to true forms of either, making them appear atypical.