We are talking past each other.
My point about the ISJ was that Introverted Sensing DOES access external information.
Show the ISTJ a pencil, he will see it, but when you ask him to reflect on what a pencil is. He will think about his personal reflections about the pencil.
The ESTP will think of his experience of observing the pencil directly when asked.
Again, let me have Jung state this point in his own words.
"Although the introverted consicousness is naturally aware of external conditions," Psychological Types. P373.
Pause right here. Think of this sentence careful and how it relates to what I wrote above. Internal consciousness IS aware of the external environment.
This means that Introverted Sensing and Introverted Intuition can collect information about the external world by virtue of being perceiving functions.
"...it selects the subjective determinants as the decisive ones. It is therefore oriented by the factor in perception and cognition which responds to the sense stimulus in accordance with the individual's subjective disposition. For example, two people see the same object, but they never see it in such a way that the images receive are absolutely identical. Quite apart from the variable acuteness of the sense organs and the personal equation, there often exists a radical difference, both in kind and in degree, in the psychic assimilation of the image. Whereas the extravert continually appeals to what comes to him from the object, the introvert relies principally on what the sense impression constellates in the subject." Psychological Types P.374
Let me draw an example for you.
A dominant Introverted Intuitive and dominant Extroverted Intuitive read Kant. The text says for example, noumenal world is in experiencable and infinite, phenomenal world is finite and experiencable.
The Introverted Intuitive makes an assessment of what is read. Associates the idea with where else he heard the worlds noumenal, infinite, finite, phenomenal, etc.
So the Introvert appeals to his world of ideas when collecting and establishing information. When asked what the noumenal and phenomenal are, the Introvert will look to his association of thoughts to give the answer.
Yet the Extrovert will simply reminisce about his direct experience. When asked to describe the noumenal and phenomenal, he will not look back to his long chain of thoughts, but will simply think about the time he has experienced acquiring such knowledge, of the time he first read Kant and will simply state what he saw.
Hence, my claim is Introverted Perception does indeed have access to the external world, yet it interacts with the external world not directly but through its own scope of perception. It interposes such an entity between itself and the external world.
Concerning your question about Ne and Se. Consider the following. In order for Ne to process an idea, it must access the idea through the senses first. You must either read about it (see it), or hear someone explain it to you verbally. (hear it)
As an allusion to my previous point, not only Se can have you hear and see, but Si can as well. This is the claim I've made in response to your first post.