(Replying to @Golden.Rose.54)
Microlabels aren't defined by how many people use them. Microlabels are defined by being a sub-category of a larger identity. In order to be autochroisexual you have to be asexual/ace-spec. So in this case someone would firstly be asexual, and could also be autochroisexual- a specific sub-type of asexual.
Basically think of it like "not all asexuals are autochroisexual, but all autochroisexuals are asexual." If you can do that then it's a microlabel.