I find this to be a disturbing trend. I don't want gray water sitting in my toilet.
Look, it's been sitting down there in that tank for who knows how long, festering and feeding on whatever nutrients come it's way, creating a literal cesspool of bacteriia and other noxious bugs and I just don't want that stuff anywhere near my possibly infectable access points. Just a little splash and you get to enjoy all the possible benefits from that region, thank you but no. Just no. An outhouse would be safer.
Jim