Key motivations, according to Enneagram Institute: Want to be self-reliant, to prove their strength and resist weakness, to be important in their world, to dominate the environment, and to stay in control of their situation.
Competence, according to Google: Having the necessary ability, knowledge, or skill to do something successfully.
I would say over half of those traits have competence at their core, versus the five, who content themselves with only the "knowing" part of the equation. For eights, perhaps it does grow contingent on itself, that because it is driven towards competence it is self-assured that it is competent. But I don't buy into the inherent "control" aspect eights are known for any more than another type can become.
A race of eights, strong and individualistic.
Though I am curious, if 1, 3, and 5 have been labeled the competency triad, what are the other two groups labeled in this system?