This is a good question, and one to which I don’t have a complete answer. Censorship in Japan has so many gray areas!
If you look at the sample images for Animal Synchronicity 1 on Rainbow Shoppers, both the English and Japanese versions are uncensored. However, the sample images on Digiket, another (more widely known) Japanese-hosted site, are censored by Mosaic, as are the sample images Kaz posted on his own blog. Why does censorship apply in one case and not the other?
I think it might be a case of the vague, archaic Japanese obscenity law Article 175 mainly being enforced towards products that are sold in physical stores. Online stores are perhaps more willing to take liberties with censorship. Also, Animal Synchronicity 1 is essentially a digital doujinshi, not backed by a big publisher that might be more fearful of prosecution.