Yeah,I ask because I'm not an opera expert either,I was just wondering.Being a singer,even though not an opera singer (and don't plan to be ;)),sometimes I wonder what's all this "they aren't true contraltos anynomore" thing.By your definition I could be one and I don't feel exceptional at all,but again I don't sing opera,so I guess that in opera,women singing like this are more rare...maybe all true contraltos go to sing some different kind of music...;)that's why they're rare.