Roy Lewallen, W7EL wrote:
"A real analysis of energy flow involves calculating the power at
various points and times in the circuit or transmission line of
interest."

Yes. Bird Electronic Corporation has done a good job of this with its
"Thruline" wattmeter for several decades.

Its practice is to measure in a 50-ohm Zo resistive lossless impedance
environment where forward and reflected waves are 180 regrees
out-of-phase. This allows Bird to say:
"Power delivered and dissipated in the load is given by:
Watts into Load = Wforward - Wreflected"

I would not argue with success.

Best regards, Richard Harrison, KB5WZI