I mean like, a Frisk is most likely younger than 9 or 10. Toriel hold their hand as they walk, she reads them stories, etc. Frisk probably wouldn't even know what transgender MEANS is what I'm trying to say.
Like, what's the thought process there?? I just??? "I think it's a good idea to ship two genderless children! Oh yeah, and one of them is literally DEAD-"