Richard Clatk, WB7QHC wrote:
"This is, of course, contingent only when the line is terminated in its
characteristic Z."

Lines terminated in Zo don`t produce a reflection at the load. I did not
make up the fact that the line forces the current to be exactlly
in-phase or exactly out-of-phase with the voltage across the
transmission line. I got it from Terman. On page 86 of his 1955 opus:
"---This differs from Eqn (4-8) (Zo seen by the incident wave) only
by the negative sign, which arises from the fact that the current in the
reflected wave travels toward the generator whereas the current in the
incident wave travels toward the load.

Zo is a RESISTANCE. In a resistance, current is in-phase with its
associated voltage. Waves traveling in either direction on a line see
the same Zo.

Best regards, Richard Harrison, KB5WZI