Or maybe he wanted to test his program first with a synthetized voicebank before attempting the human-voiced one's experiment.... And then with growing popularity and such ad working on it, he may not have had the time to test it himself /shotdown
Or, maybe he does have a voicebank; but had never released it to the public. Or, possibly, he has a voicebank, but his ownership is under an alias. (secretly, that is.)