Yes it ties the IDC of the water and fuel. So if you see max 80% fuel IDC, then your max water DC with the 2D kit is also 80%. the HSV valve is driven by the fuel injector switched ground. You can't change that.
In the tables/graphs the listed water jet flow is at 100% DC just like the fuel injectors flow are listed at 100%. What the water jet flow at 80% DC will be - I doubt anyone can answer you that and you can't find a table listing it. Probably your best choice is to make a setup which triggers the wire at 80% DC and measure the water flowing
