Not quite sure I phrased it right in the title but basically:

1. if autism presents differently in men and women (which is what I've heard said -- I don't know if this is true, or how it presents in nonbinary ppl), and
2. we don't understand autism's underlying causes (do we?)
3. what's the basis for classifying autism as a single spectrum, rather than two (or more) different things?

I assume the differences in presentation between genders are differences on overlapping averages and not absolute, but even allowing for that we could ask the same question, how do we know that typically-male-autism and typically-female-autism are part of the same thing?

Genuinely curious about this, don't mean to suggest I think our system of classification is wrong, I just want to understand.