Bob,

Sorry for the strong words, but the intent remains the same.

I don't know what happens to the source impedance when the load is
changed, because the system is undefined.

However, read carefully the definition at the beginning of your paper.

The Maximum Power Transfer Theorem:

The maximum power will be absorbed by one network from
another joined to it at two terminals, when the impedance of
the receiving network is varied, if the impedance looking into
the two networks at the junction are conjugates of each other
[1]