Nor is it sold as a complete game, that's a falsehood, there are disclaimers all over the place before you buy that it's an alpha and it will have bugs.
You've got complete and unfinished mixed up. It's not sold as a finished game, but it is sold complete in that it's the only payment you need to make for it.
I wouldn't say the website's full of disclaimers either. The front page mentions potential instability at times, and the purchase graphic says you get 50% off during alpha. That's pretty much it. If there's a line somewhere about how he reserves the right to release updates without trying them out first because that's what the paying public is for, by all means, point me to it.