There ya go, the decision is not really a part of SA but a product of.
Something is only a product of something else if it's a separate and distinct mental process. Which in real-time SA and reactions to it are usually not. While cogitating about it after the fact may make it seem that way or may make it easier to dissect retrospectively for analysis, that is the actual reason Endsley gives for arbitrarily choosing to unlink the two, not because they are necessarily two different and distinct mental processes. Certainly if a person really worked at it they could mentally divorce or override the observations from the brain's automatic connection to a most prudent decision, but in combat, especially air combat, that could be relatively time-consuming and therefore unhealthy. The only time SA/Decision would truly be separate, as Endsley talks about, is if you consciously overrule the automatic decision made immediately by your brain with a different one for reasons outside of the realm of SA (force of personality, deception, unpredictability, etc.).
It's like smelling freshly baked chocolate chip cookies and deciding the instant you smell them that you want to eat those chocolate chip cookies. While there is an instantaneous cause and effect relationship there it was only insofar as the brain connected a stimulus to a decision in one action, it wasn't a consciously formulated decision. That's how the brain works, real-time sensory information doesn't just sit in a holding tank patiently waiting for us to cogitate about it and contort it into a decision, it actually causes a decision to fire in the instant of perception. It's part of our survival instinct we gained through evolution sometimes combined with contextually driven conditioned responses.. There was no separate cogitation, "Hey I smell cookies..What should I do with them? Should I eat them? Should I shove one up my bum? Should I throw them at my cat?"...
The act of smelling the cookies and the decision to eat them was one fluid mental motion, stimuli>decision. If you ever get the chance watch someone getting a PET scan, you can actually see this happening in real-time. It's quite fascinating, it looks a lot like lightning dancing in a cloud lighting it up.