Spectrum in some uses does not imply having 'ends'. In most uses, it does imply a line from one end to the other.
Continuum would be a better choice, but it still implies a line with directions towards something in each direction.
I have imagined non-binary as a three dimensional space, without an end in any direction.
As a non-binary, you could be at any given point or really as many points as you want, at any given moment.
Somewhere, there is the point 'male, and there is 'female'. They don't necessarily have to be stationary points.
You could draw a straight line between the two and call that the binary spectrum or continuum.
I don't think that is correct, I think any individual moving between those two points can also be at other point(s), also.
But there is the intention of moving from one place to another, but why not also be at other places at the same time, too?
Just speculation, mind you. Spectrum or continuum are simple ways of looking at it, effectively.
A space does open up possibilities that are hard to define with a line.
Adding time or not has an effect that could be used to define the possibilities.
Ativan