Cecil Moore wrote:

My comment above is primarily about standing wave current,
not about coils. Standing wave current phase cannot be used
to measure the phase shift through empty space, wires, or
anything else.

Sure it can. You just haven't yet figured out how to do it.

Here is a hint.
Standing wave current and voltage is not all the same phase.
Go far enough down the line, and there is a change.
How far is far enough?