Cecil, W5DXP wrote:
"Nope, it`s not. (phase difference between forward and reflected waves
locked in phase)."

At any specific point on a transmission line, the phase angle between
the incident and reflected waves is unvarying. That`s what makes
standing waves.

At any specific point on a transmission line, the incident wave arrives
a fixed number of degrees after its departure from the transmitter.If
there is a reflected wave it is delayed by the time it takes to travel
the route of the incident wave, plus the delay in traveling the
aditional path to the reflection point. Then, either the voltage or the
current is going to experience a phase reversal upon reflection. If the
load impedance on the transmission line is too high, the current
undergoes a phase reversal upon reflection. If the load impedance on the
transmission line is too low, the voltage undergoes a phase reversal
upon reflection. Then the reflected wave still must take more time to
come back from its reflection point to the point "P" on the line where
we are considering the phases and magnitudes of the incident and
reflected waves.

Terman says on page 95 of his 1955 4th edition:
"However, irrespective of the relative amplitudes of incident and
reflected waves, the phase of both voltage and current will advance
exactly pi radians (180-degrees) when the distance toward the generator
decreases by a half wavelength. Although in the absence of a reflected
wave the variation in phase is at a uniform rate within this distance,
this is not the case when a reflected wave is present."

Terman is looking at the sums of incident and reflected waves above.
Back on page 89 he was considering incident and reflected waves
separately when there has has been a reflection from an open circuit.
Terman says:

"Consider now how these two waves behave as distance l from the load
increases. The incident wave advances in phase beta radians per unit
length, while the reflected wave lags correspondingly; at the same time
magnitudes do not change greatly when the attenuation constant alpha is
small."

Terman is saying that as you look at points closer to the generator you
aare looking at the emerging wave sooner in its history, but for the
reflected wave the same points show the wave after it has more history
paradoxically as you move closer to the generator.

Best regards, Richard Harrison, KB5WZI