Indeed, I see in your pictures that the diameters of the two coils are equal, which means that there remains no slack in the nub. I had not loaded your loop so much, and that is why the second / higher collar remained more loose.
However, I still believe this second collar is an overkill. We use two collars when we want the friction between their parallel and adjacent wraps to keep them "locked" - but here you have the nipping loop itself to do this. I do not believe that two collars grip / nip / immobilize a penetrating line more than a single one ( and, in any case, such an effect, if it exists, it has not been demonstrated by any test, ever ) - because one single collar "bites" harder into the surface of the line, but two, although they provide a more extended area of contact, they also provide a more extended area on which a line can slide, because they can not penetrate into its surface so deep.
I think that if you tie the much simpler knot I had shown in my previous post ( with the vertically oriented coil, which is loaded more directly by the returning/second eyeleg ) you will see that it is no less tight and secure, although it uses one, only, collar.