I agree with all you said but I just question whether this is dehumanization. I don't really think dehumanization is a useful term because it's so unclear what it means.

In horror movies, the characters don't act like people would act and are portrayed in ridiculous ways, but I don't think all horror victims are dehumanized because of that. I think the problem in porn is more that sometimes women are depicted as enjoying things almost all women would not enjoy in real life, and this is sending a bad message. But I don't think it's dehumanization.

And I don't really think it's true that the audience doesn't think women in porn have their own thoughts and experiences. I feel like the abundance of fake moaning is testament to the fact that they care quite a bit about the women's experiences, but it's just in a limited sense. They usually don't care about the women's experiences outside of a sexual context. But I feel like that's more just being unempathetic than being dehumanizing.