Cecil, W5DXP wrote:
"Let`s look at the following system with two sources,"

Is this tempest about creation of an oppositely phased wave to cancel a
reflection?

A way to avoid reflected waves within a waveguide is mentioned by Terman
on page 148 of his 1955 edition:

"Create a reflected wave near the load that is equal in magnitude but
opposite in phase from the wave reflected by the load; in this way the
two reflected waves cancel each other."

"Some of these (matching arrangements) are analogous to the impedance
matching arrangements employed in transmission lines (described in Sec.
4-11) while others are unique to waveguides."

Best regards, Richard Harrison, KB5WZI