Keith wrote:
"At these minima, rather than the energy flow being 0 as it is for an
open or shorted line, the energy flow (power) is exactly the energy
being delivered down the line."

The power is not zero at an SWR zero, provided that the line has power
flow. The power flow at the specified null is equal in forward and
reflected wave directions as shown by the complete zero.

Power delivered by the source and to the load is the forward power minus
the reflected power. In the case of a complete reflection, the
difference between forward and reflected power is zero, so the load is
rejecting all the forward power, which is turned around and becomes the
reflected power.

In a lossless line, forward and reflected powers flow unabated from end
to end of the line and are thus have their same amplitudes wherever they
are measured in the line, including SWR null points.

Best regards, Richard Harrison, KB5WZI