My Postulate
Electrons move at about 1 meter per second in an AC impressed signal cable. Mostly they just jitter back and forth, under the control of an information packet we usually call "signal". A signal is comprised of E Field and B Field, with E Field being the moment when the signal changes vector. At this moment the electrons holding the signal twist the axis of an electron, attached to a dielectric end atom, to the obverse of the spin and axis of the holding electron. This in turn causes the equivalent electron on the other end of the open chain of atoms, comprising the dielectric molecular structure, to twist to match the holding electron. Incidentally, this his is how AC signal is transferred across a dielectric barrier.
This momentary hold for vector change is controlled by the charge threshold of the dielectric material and the subsequent release threshold and the time between these two appears to be affected to a degree by how many electrons can be signaling within a given area. This later is referred to as "dielectric constant". Holding electrons, without sufficient charge to affect the electron on the end of the dielectric molecule's atom, are lost from the coherent signal. The release threshold also provides a time interval to the resumption of the AC signal as a B Field event. These three events all contribute to the loss of signal coherency on the return portion of the signal through the load.
The loop of wire, as a shorted turn comprised of many strands of insulated wire in my usage, coated with a two part dielectric material, polyurethane and nylon, has an extremely low RAC and RDC, but it's useful path length is very long, when considered as an unterminated wave guide. The entire loop is at a lower state of impedance than the ground it is attached to and over a period of time actually fills the open orbits of the empty orbits found in the copper wire. Due to the triboelectric effect of the additional pieces of dielectric, in the official Ground Control, maintains this "filled" capacity, so long as there is a source of electrons to replace those that trickle away.
After attachment, those low level wide band signal components will be maintained in this unterminated wave guide. Meanwhile, being lost to poor dielectrics and boundaries between different pieces of metal, throughout the ground system provided, out to the local pole in the ground itself. I suppose we could claim quantum choice effects here, for the signal, as it moves at the speed of light through the pieces of wire involved in this, but I don't really think it's necessary to argue at that level.
Your notice of greater dynamic range is most likely just a drop in the noise floor and more coherence to the originating signal of information, on the back half of the signal waveform. These two are linked, since signal dropped from the "information packet" of a coherent information data stream will become a random event and cause random charged electrons to pass the information back through the load as noise.
Bud