Quixel blend materials for vertex painting

hey guys, I’m having troubles with blend materials imported from the bridge. When trying to use them in vertex painting they dont seem to be assigned correctly to the RGB channels. for example, I will blend 3 megascans surface materials and in vertex paint, no matter what channel I switch to only 2 of those materials will be paintable one channel will be a duplicate. Also, I’m having a hard time to understand which channel and how can I assign a liquid layer to for painting puddles? Is it random or how do I set it up to be used on a specific material channel?
I uploaded a gif video of what I’m talking about