Intersex is an abnormality. Sometimes it is abnormal presenting genitals but the person has either xx chromosomes making them genetically female or xy chromosomes making them genetically male. Sometimes the abnormality is chromosomal and you have someone who is xxy for example. Or xo or xxx (I googled that to double check)
Trans people as a group have to the best of my knowledge no chromosomal abnormality that has resulted in them being trans.
Intersex is an abnormality. It does not mean that there are more than 2 sexes. It means that sometimes things go wrong during foetal development.
Sometimes babies are born with missing limbs or extra limbs.
Does this mean human beings limbs exist on a spectrum and we are designed to have between zero and ten + limbs? No. It means sometimes there are issues during foetal development.
There are conjoined twins. Does this mean the range of the number of heads humans are designed to have is on a spectrum? No. It means that sometimes things go wrong during foetal development.
People exist that are different. For a variety of reasons. Those differences do not transform the biology of humans into a spectrum that developmentally and biologically has evolved to intentionally (evolutionarily speaking) include them.
It doesn't mean people with physical differences matter less or are less deserving in any way. It simply means that they don't form part of what is the intended biological template of the species.
I've got an extra nipple. Lots of people have. It's quite common.
Nipples aren't on a spectrum.
There's two nipples and there's developmental error that has resulted in some people having extra nipples.