Is the Esdaile state of deep hypnotic trance exhibiting a part of the deep subconscious, or is it, perhaps, only at the border?

Being "at the border" is a good description. It is a state that is the deepest that humans have explored deliberately and been successful in experiencing, but it is on the side of the border as part of the upper subconscious and not the deep subconscious. So that is a categorical and absolute point of differentiation, that people cannot get into their own deep subconscious unless they do so intuitively, as you do in your channeling.