I understand your explanation and why it would be a theory but at the same time there's evidence to suggest otherwise. If Kaguya had a child with a human then her children would have human features like Indra and Ashura but that wasn't the case.
That point is entirely wrong and invalid.
You really don't seem to understand genetics.
Indra and Asura are Kaguya's grandkids, not her kids. That is why they were more likely to look like humans than their father. You can not use them or the Hyuuga clan as a reason to support your invalid point.
Hagoromo and Hamura were Kaguya's kids, so it would be natural for them to look much more like Kaguya than Indra and Asura.
They don't need to look like humans to have human blood. I reiterate: Gohan had a tail and he can go super saiyan and he has the spiky hair of a Saiyan, but he is still half human. Sarada has Sasuke's black hair and the sharingan (and she doesn't look like Sakura), but Haruno blood still runs through her veins. Boruto has Naruto's blonde hair, blue eyes and even the whiskers (and no white eyes), but Hyuuga blood still runs through his veins. Etc...
Please learn this concept. A person's physical appearance alone does not dictate what their bloodline consists of.
Have you really not seen or heard of a child that looks much like one parent and nothing like the other?
I can't stress this enough. Stop assuming people's bloodline based on physical appearance alone.
Also, I never said the person performing chibaku tensei was a human. I said it was likely a supernatural being like the shiki fujin.