I'm a bit more of a purist, so I don't consider a synthetic aoto an aoto at all or the 2k green brick called an aototoishi (aoto sharpening stone). An Aoto is an aoto, much like real whipped cream isn't cool whip
Aotos are actually a whole CLASS of stones. Strictly speaking they are not considered as a middle grit stone or nakado, but are their own class. They do largely overlap the nakado in grit range so very casually speaking they can be considered mid grit stones.
There are a number of types of real aoto - Aono, Wachi, Konusuke, Saiechi, etc and closely related Monzen - not formally classified as an Aoto but for all practical purposes functioning as an aoto. Within each group there are varying hardness levels - typically medium or soft. They tend to be characterized as producing (obviously) a natural stone finish, and capable of continued refinement as one works the mud, unlike synthetic stones. They tend to give a somewhat toothy edge, one that is held in high esteem for butchers and others who do slice cutting type tasks. They are an excellent middle grit for single bevel knives, awaiting further refinement with finer grit soft stones like a Hakka Tomae.
The type of edge is best appreciated by taking a paper towel rolled up and seeing how it cuts the rolled up towel quite aggressively.