Yeah it's the first time I've heard of it referred to as a spectrum. Although the term is insensitive it's more like two sides with a few outliers.

You have your XX females and your XY males making up 99.9% of the population and then some individuals who are XXY, XYY, or XXX. You can even have some who are XXXY, XXYY, or XXXX.

In terms of how that affects biological sexual development and associated gender identity i can't say offhand and it would likely be a rabbit hole that one can spend hours looking into.