Some water does have taste. Would I consider something absolutely pure without any kind of taste to have a taste? Not sure, probably not, but I don't see the correlation to Athiesm.
I don't think athiesm is a religion per se, but its a belief system as are religions. Its a trust and a belief in the notion that all things are explainable through natural laws and there is nothing outside of those natural laws.
There are other belief systems that also aren't religions. For example, someone that believes we are simply the results of a genetic experiment by aliens, or that we are simply an alternate reality that is nothing but the dream of some other being, are both belief systems that also doesn't have any semblance to traditional "religion" as its commonly used.
I would actually say your agnostic types as being the closest to no taste. The people who simply don't know whether or not there is a god/supernatural/higher being/etc and simply don't care, holding no real belief in it existing or not existing.