Roy wrote, "... That is, the coil is capacitively coupled to ground,
and this
causes displacement current from the coil to ground."

In fact, if there were no such current -- if there were no capacitance
from the coil to the world outside the coil -- then the time delay
through the coil, calculated from tau = sqrt(L*C), would be zero. It
is exactly this current that allows there to be a transmission-line
behaviour and a corresponding time delay.

That's not to say, however, that a physically very small loading coil
with practically no capacitance to ground would not work as a loading
coil. It just wouldn't have a transmission line behaviour worth
mentioning.

It is also exactly this displacement current from a large coil that
allows the current at one end of the coil to be substantially different
from the current at the other end.

Cheers,
Tom