Well I realized that part of it is because most type descriptions don't understand the core wound of 9 at all. Sandra Maitri's is the only one that does this to a significant degree.
I think the connection between 9 and 3 often gives 9s a sense of being 'private 4s.' Often hating and envying people for not being able to live up to their own potential. The fear that you're not allowed to be who you are, that you have to hide yourself and not draw too much attention to yourself.
9s generally act very easygoing and nonchalant on the surface. But deep down they long to be seen as very special people, and suffer deeply for their specialness being unrecognized. Deep down, 9s feel supremely ugly and that they will never be truly loved - that love, goodness, happiness and fulfillment is not for them, but for other people. 9s go numb and passively dead because they are covering over this deep sense of being eternally unloved. They long to be loved but don't feel that it will ever be possible for them. They become hopeless and resigned to ever being truly seen for who they are.
There's the internal sense that other people won't let me shine. Compared to others you are subtly inferior and never able to fully be yourself. More than any other type, 9s are still identified with being a little boy or girl in a world of big grown ups that belittle you and don't acknowledge you as a full human being in your own right. So you slink into the shadows because you are unseen as god made manifest.
We live in a world where people are asleep to the essence that lives in every human being.
The childlike innocence and underdeveloped ego of the 9 gives them a greater access to an objective perception of reality, that we are all one, that we are all god, that we are all nature, that life is inherently beautiful and full of love. But they often fail to ever grow up and embody this in a real way. Often they live in the dream of oneness that they remember from childhood, and their attachment to the child's experience of essence causes them to never really want to grow up.
There is the quality of the puer aeternus to 9s, because they remember the magic of childhood that was infused with essence. They don't want to grow up because they want to remain connected to their essence through memory and imagination. They don't want to enter the world of grown-ups that have become so hopelessly out of touch with their essence, so they fail to develop a real sense of themselves as a mature human essence. Often this can take the form of attachment to early childhood relationships and beliefs, but under the surface it is the desire to remain in touch with essence.
9s fail to develop their essence when they remain attached to childhood experiences of it. 9s need to see that they are never really disconnected from essence, and that growing up and developing themselves as a person will never disconnect them from the ground of being that they desire to remain in touch with. 9s need to realize that they themselves are the ground of being become manifest through form, and that living a full human life deeply in touch with themselves is the most complete way to remain in contact with the world of essence.
9s don't fully inhabit their bodies because they are still identified with having the bodies of little children. The message they received as children was to suppress their natural instinctual energies, and this cut them off from the natural growth of their organism. To regain access to essence, 9s must re-establish contact with their instinctual energies, and awaken to their presence as physical beings in the universe.
On a subconscious level, 9s are still identified with the non-existent source of all manifestation, the non-being prior to being. 9s need to awaken to the fact that they exist in this world as the expression of the absolute nature of reality. This means realizing that they were born, that they are human, that they have a body, and that their body and their sense of self is the greatest gift to the world. They don't need to hide in fear of existence any longer.
Awakened 9s overcome the feeling that their existence is completely inconsequential. They realize that they are an intrinsic part of the whole universe. In fact, they realize that they are the center of the universe, and that the entire universe was created for their glory and their enjoyment. When 9s awaken to themselves, they know that they are no longer overlooked and unloved. They see that love is their very nature, and that they can never be separate from the source of all bliss. They realize that they are deeply divine beings.
When 9s awaken to this truth, their life no longer consists of a constant state of unfulfilled numbness. They realize that all of creation is a constant flow of light, love, pleasure, and bliss. They no longer become numb to the pain and struggles of life, but realize that without these uncomfortable growing pains, the joy of existence would have utterly no meaning. 9s begin to truly embrace everything, from the deepest agony of life, to the greatest heights of ecstasy.