Elementary, my dear xarax… 
After a night s sleep, I awake with a completely different mood - with no more questions, but with some (tentative) answers:
I thought of the exactly opposite situation : Let us have a proper “knot”, a knot s nub, and penetrate it from the one to the other side with a main line or a pole, loaded through both its ends. Will this “knot” become less of a “knot” ? No, it will be simply an ordinary “knot”, just wrapped around a “neutral element”, regarding its own function. We can now imagine that the cross section of this main line or pole expands, and widens, forcing the "knot’ to widen along it ( because it would have to remain tightened around itself, AND around the main line or pole ). So, what will this "knot : become ? A hitch !
I had already thought of this “thought experiment” , albeit in a slight.ly different context - but, to my surprize, I had not made the small step needed to actually define what a hitch is, starting from the already conquered ground, the image of the tight, dense, minimizing ropelength tangle we use to call the knot s “nub”.
The interested reader is kindly required to read the following lines, replacing the “neutral element” with “main line” or “pole”
One is not obliged to concentrate about the question of the TIB or not nature of the "surrounding knot", as I had done in this paragraph, which is only of a secondary importance ( a TIB or not TIB hitch, is a hitch nevertheless ). The “surrounding knot” is a not but a knot s nub, a proper “knot”, in the case the diameter of the main line or pole shrinks to zero. We are not allowed , of course, to alter the topology of the hitch, that is, no segment of the hitch can cross this axis of the zero diameter cross section of the main line or the pole. Therefore the hitch is bound to be knotted, literally, around this axis, and it is nothing different than a proper “knot”, what most people would call the nub of the knot, the local, tight, dense part of it.