Transmasc Kris this, Transfem Kris that, has anyone considered intersex Kris, they're nonbinary so they could still be counted as trans, but like. Why has no one considered this, at least that I've seen. It would make so much sense for them.
Also on top of it, you can make angst fic or art of Toriel and Asgore struggling to understand how puberty or their hormones work because they want to best support their kiddo, but many books on humans in the delta-verse(deltarune game) have no information on intersex people, so it makes it harder for them to parent Kris to the best of their ability.
It would also add another layer of Kris feeling out of place, because even if they met another human, they probably wouldn't understand Kris' struggles or be able to help them understand what's going on with their body as they continue to grow up.