What is missing here, IMO, is that the physics of energy flow has not
been adequately explained. Cecil provided a reference to it but did not
elaborate for the general readership.

The energy in forward and reflected waves has been well documented for
many years. From Kraus, Electromagnetics, McGraw Hill, 1953, Chapter 9,
Section 9-13, "Energy Relations in a Standing Wave":

EQ 9-145 We = 2eEo^2[cos^2wt*sin^2Bx]

EQ 9-147 Wm = 2uHo^2[sin^2wt*cos^2Bx]

Note: The energy in the E field [We] is a function of the sin^2(Bx).
The energy in the H field [Wm] is a function of the cos^2(Bx).

You will remember from trigonometry the the maxima [or minima] of a sin
and cos are displaced by 90 degrees. Conclusion: when the E field is
zero the H field is maximum; when the H field is zero the E field is
maximum. Ergo! Energy is conserved and propagates through the zero E
field as an H field; also, when the H field is zero the energy is in the
E field. This is what Cecil is referring to when he refers to the
Poynting vector.

It is analogous to a parallel tuned circuit. When the instantaneous
voltage across the capacitor is zero we don't claim there is no energy
in the circuit. We know that the energy is stored in the inductor.
Conversely, when the instantaneous current in the inductor is zero we
don't claim there is no energy in the circuit. We know the energy is
stored in the capacitor.

In a TEM wave the energy cycles between the E field and the H field and
the energy components are 90 degrees out of phase.

Deacon Dave, W1MCE