Richard Harrison wrote:

"Transmission Lines, Antennas, and Wave Guides" by King, Mimno, and Wing
is an excellent reference, and like Terman, the authors agree with
Walter Maxwell. On page 43 is found:
"Principal of Conjugates in Impedance Matching - If a dissipationless
network is inserted between a constant-voltage generator of impedance Zg
and a load of impedance ZR such that maximum power is delivered to the
load, at every pair of terminals the impedance looking in opposite
directions are conjugates of each other."

And can be seen clearly by looking at the reflection of a smith chart
upside down.

Best, Dan.