Board Thread:General Discussion/@comment-24100805-20160201152915/@comment-35640811-20180316112341

TheHumanAmbassador wrote: Frisk IS gender-fluid, because they're whatever gender you want them to be. Just like they're just as nice (or murderous) as you want them to be. You, the player, roleplay Frisk.

As a result, both male, female, and non-binary are all correct interpretations of Frisk. Just like Pacifist Frisk and Genocide Frisk are both real interpretations of Frisk. And Cinnamon vs Butterscotch.

Of course, since "they" is normally used when gender is unknown, the game uses it, and the Wiki also uses it for articles, as to not take sides, which would break the neutral point of view. They're not genderfluid, since the only player in the game is you; Im not even sure their gender projects onto you, unless you wanna believe that hard.

The Wiki not only uses they/them because of neutral point of view, also because Frisk's gender i uncertain.