water wetter is to mix with distilled water in place of coolant. Mix it with coolant and it doesn't hurt bike. The point is to remove coolant from the bike, so that if you go down on the track the slippery coolant doesn't mess it up for everyone else.
I understand the point. Mostly asking because the previous owner of my bike gave me half a bottle of water wetter with the bike and then when I noticed the coolant was low a few months later I used regular coolant and never thought about how that might mix until now, heh. I've read of some different types of coolants that will gel if mixed with normal coolant.