It seems that there are many things to be discovered still, but step be step with experiments and researches the vision is becoming clearer. At this point i guess that the magnetic current and wave propagation are cause of many of this effects. For example the fase shifting in Naudins experiments suggest that there has to be a quite slow propagation of the magnetic wave in iron cores for example, in order to get a 90° shift at 30mm from the exiter coil. Maybe it is related with the frequency capability of a given core material. It would be very interesting to test different core materials.
And as you stated i also beleave that the coil itself plays an important rol too. I saw a video from Thane Heins where he explains the coils function in his regenerative acceleration theory (REGEN-X), where he declares the cause of the retarding to be the distributed capacitance of his coils. This is in my opinion not likely , as the distribute capacitance in a coil with 2.5ohm , in the best case bifilar won't have that much capacity to cause a 90° fase shifting at a typical rotating speed of a generator. But it could have an influence in combination with the core.
In contrast in the case of a hi frequency air core transformer i can imagine that distribute capacitance plays a mayor rol ,and can certainly cause delays of the required magnitude.
Regarding the fase shifting in transformers I have to confess that i don't have much knowledge and experience in this field, but i would like to learn more about it.