Like all info elements, Se is something you can see in behavior and feel psychologically.
In Se egos, Se is something you see manifested in someone's personality continually, i.e. nearly all the time... (Like Ne in your ego and Fe in mine...) Thus, "Se leading."
Socionics describes personalities via how they process info... The only way one can detect how people process info is by observing their personalities, (e.g. psychological "traits,") to see and feel how the info is manifested in their personalities. ("Manifested" = what you can see and feel it in a person's personality.)
I am a practical man and thus content to know Se (and the color purple, for that matter,) when I see them and feel them, i.e. I am content with Socionics, unpolluted by the enneagram.
This is all by way of saying, you and Socionix are abstracting Socionics--something meant to be tangible and experiential--to the point of being impractical, ineffable, and signifying next-to-nothing to real people in the real world.