Who cares - you shouldn't be running it with a leaking system unless you are Richard Branson, so really it doesn't come into the equation in my view. If you look at all the other lubricants in your vehicle none of them will aid the expansion of a remote platypus population, so toxic or not, simply another fluid which is treated with respect.

I agree with your comment about the efficiency as its nigh on impossible to remove all the water unless you go to a heap of trouble like draining, blowing thru with high volume/low pressure air and then maybe heating the block or blowing hot air thru to dry it out. There is no indication of the cooling efficiency drop per % of water either - doubt they even know. I am going to have a look at the other 'product' with 'nano particles etc etc blah b;ah blah' and see if I can find a product that is cheaper to swap with better cooling properties than the glycol mixes.