Cecil, W5DXP wroyte:
"Why doesn`t the same thing happen 1/2WL back up the line where the
impedance is exactly the same?"

Uniform distribution of inductance and capacitance 1/2WL back up the
line.

John E. Cunningham in "The Complete Broadcast Antenna Handbook" wrote as
I recall, an attempt to explain the reflection operation on a
transmission line as caused by impedance discontinuities.

If I recall, he said a short on a line vitiates capacitance at that
point. It shorts it out. Increased current in the final segment of the
line inductance sets off the reflection. The extraordinary volts
generated, reverse the wave direction and reverse the phase of the
volts. What happens to the current is a turnaround sooner than later,
but it still comes and goes in the same phase.

The discontinuity is essential to the turnaround. Lacking a reduction
point or growth point in inductance to capacitance ratio, you lack an
essential to generate the reversed signal. That`s why the virtual short
does not turn the signal around. It has no discontinuity.

Best regards, Richard Harrison, KB5WZI