Bags of akadama say "fired" because by law it cannot contain any organic material as it is imported from Japan. If the Feds found out soil that has not been nuked into oblivion was being imported into the US, Akadama would be the the soil component "we used to use".
Al says it's kiln dried. I don't know how hot that is, but I have opened bags of Akadama and found dead whole ladybugs, dead snails and lots of little twigs, so It can't be exposed to too much heat. As Nate said, if it was cooked, it would only be good for water retention and lose it's Cation exchange capacity which is already relatively low compared to organic material, which most people won't use.
I think the key is inorganic soil of the correct size. pumice for water retention, lava for air and heat retention, and akadama or kanuma for cation exchange (in other words, Boon's mix).
Last year, I was thinking large particles for large trees, med for med, and small particles for small trees. Ryan pointed out to me that the functional part of the root system on a tree is about the same size, no matter if it's a huge tree or a shohin, so soil should be the same also.