I wouldn’t try and bake dynamic-branching in if I could help it. I know I’d likely end up making a costly mistake.
My comment is more to the point that when I do my regular-maths, LERP things and the like, there will be points where the alpha of a thing is wholly 1 or 0. IF it’s technically possible, being able to ‘foresee’ that and only run the one/other input, to my mind that could be a savings, but I’m not a dev in this area. No idea if it’s at all logically/mechanically possible. The idea here is that the engine might find a way to save overhead at runtime, even if I cannot predict such up-front.
Think a slope-mask. At some point it’s all one thing or all another. In between, sure you run both paths b/c you need to mix between the two. Otherwise, for the bulk of the work it’s either/or. IF the engine could create a savings there, that would be nifty.
As for the node, I am guessing it’s simply ‘you can have both sides of this boolean-switch and have access to the on/off paths at runtime w/o needing to recompile’, like a best-of-both-worlds thing. Who knows, maybe it’s keeping track of two distinct shaders and swapping them out at runtime?