Read the study.... Check the numbers yourself.
Crystallized THC(trichs) are not water soluble. But once vaporized into a gas, THC does in-fact stick to water. Maybe it never dissolves "into" the water, But there it stays trapped.
In fact I would venture to bet my entire rep bar that, the more surface area your smoke touches, the less potent it is when it gets to your lungs. That would include 4' bongs and any multi-chambered device.