An exercise designed to cultivate neigong is not a neigong itself.

Neigong exists in your body all the time.
It is part of how you move.
A habit: unconscious and familiar. As easy and present as speaking or drinking from a glass.

If you have to think about a neigong quality or practice it, or engage it when needed... what good is it in combat/application?

An exercise is a training tool.
It helps you to get the hang of the habit, to feel how it works and to incorporate the feeling into your framework.
When you have the neigong quality as part of how you move, the exercise is no longer required.