So complicated!

What if you simply said something like this:

"Are you  biologically  male, feel you are only a male, and are sexually oriented only to people who are biologically female and feel they are only female?

OR

"Are you biologically female, feel you are only a female, and are sexually oriented only to people who are biologically only male and feel they are male?"

If so you are in the binary sexual and gender part of the spectrum.

BUT

If not strictly as defined above?  Then you are outside the binary sexual and gender part of the spectrum.

I've just finished reading China Mieville's "Embassytown," in which there's an alien race that cannot lie, whose language is always literal (except for similes, which still have to have some literal anchor) and has no generic "that" -- but they have to learn, in order to deal with a particular threat.  (It's complicated and weird, like most of his novels.)

Some of the failure of communication between humans and this race reminded me of trying to explain nonbinary gender to some people.  It's like trying to explain irrational numbers to someone who only understands integers.  You have to take it in stages.