It's quite obvious the current through a loading coil tapers. As a first
approximation it's because the voltage and current along it varies according
to a 'cosine' curve as they do along any other sort of continuous
transmission line.

V and I on either side of a coil can be opposite in phase as they pass
through it.

This occurs when the length of the coil passes through a 1/2-wavelength
point. 1/2-wave points can occur at any point along a coil depending on
where the coil starts and ends along the antenna. This helps to illustrate
the action of 'phase-reversing' coils between adjacent antennas lengths.

What I find so intriguing is what the 'taper proponents' intend to do with
the 'taper' data when at last they have it in the form of numbers? Of what
use is it? Into what are the numbers inserted? What is the next stage in
the proposed modelling process?
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Reg, G4FGQ