Imagine a woven screen, with threads running perpendicular to each other. When these magic threads get wet they swell to the point that they close up all the gaps in between.
You can see this swelling when you put a few drops of water in just one spot.
So when dry it is very breathable, and wet, it is for all intents and purposes, very water resistant.
In the "transition phase" it's moving across the spectrum. In a hiking or cycling situation where you are usually "cooking off" water vapor the transition is less of an issue than one might imagine. By the time the sun is out, and you're ready to take it off, you are dry.
Not a perfect piece of science like eVent, but better than most PU and 2nd generation Gortex - IMHO, and relatively inexpensive.
With DriDucks the ploymer layer is on a spunbonded fiber scrim that is not terribly durable. In many cycling jackets it is on a much more durable substrate.