Yes, more or less. It’s a spectrum forced or pressed to the extremes, if it wasn’t, I think a lot of more people would consider themselves somewhat pansexual.
It sounds like you are making the argument that sexuality is nuture, not nature…I am not sure how I feel about that. I suppose it must be both to some and that there would definitely be significantly more gay, lesbian, bi, etc. folks if society didn’t socialize us to be hetero by default.
There are perfect zeros in the Kinsley scale, and even without the social mechanisms in place to encourage heterosexuality I’d expect them to be. I just think they would be closer to extreme cases and not to the mode.
I was playing with the word ‘natural’. Of course, everything that happens is natural, heterosexuality is as natural as homosexuality and pansexuality because it happens. But yes, I believe straight heterosexuality would be pretty rare without all the social mechanisms in place to encourage it.