The reason Swedenborg gives for this is that one’s spiritual body consists of psycho-organic forms which make up one’s true being. So angels can identify the quality of another person’s soul just by looking at their spiritual features and facial expressions.
While on earth, body language can indeed communicate some of what a person is thinking, but that same person can also learn postures and facial expressions to deceive and thwart the examination of others.
Deception is not possible in the heavenly realm. (To maintain order in the spiritual world, all individuals must find the eternal habitat and ecosystem that most harmonizes with their psycho-qualities and belief systems.)
When we leave our physical bodies behind at death, what survives is the quality of who we really are—from within. In the spiritual realm, all individuals go through a process of having their deepest thoughts and desires come to the surface. In other words, our thoughts and loves, which represent the very fabric of our soul, become the very fabric of our spiritual anatomy and reality in the world beyond this one.
People are ugly or beautiful in the spiritual world not from genetics, but from their life choices and passions. (We instinctively perceive this inner judgment of our various associates, regardless of their outer successes.)
If we are all truly connected, then we must expect a more personal sharing of content in a realm where mutual sharing and reciprocation is intensified. The way to live in peace in such an open society is to live your life with a clear conscience guided by the Lord God’s tenets.
The spiritual world is more real than the physical world. Our thoughts and desires are more real than how we dress and brush our hair. In fact, our thoughts and desires eventually become what we spiritually wear and what we ultimately look like to others.
Mindreading? We all have the potential for mindreading (because we are inwardly spiritual beings). But, the same method for acquiring such an advanced ability is the same as acquiring personal and genuine innocence.