Ron, W4TQT wrote:
"Since the voltage and current are 90 degrees out of phase, the stored
power is purely reactive but could become real diissipated power if any
resistance is reconnected to the line."

Ron specified a "half wave lossless line" with complete reflection at
each end.

Forward power into Ro creates a current in-phase with the voltage. Ro
rigorously enforces it. An open or a short at the load end of the line
creates a complete reflection in which the volts and amps are
180-degrees out-of-phase. The line again rigorously enforces it.

The only 90-degree phase angle is in the standing wave pattern.

Best regards, Richard Harrison, KB5WZI