Cecil asked,

But to what power are the transmission losses referenced when reflected
power is allowed to be incident upon the source.

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Cecil, when there are several different power levels at different places in
a circuit, it is entirely up to you how you reference one to another in dB.
It's just a matter of convenience with the particular problem in hand.

But things are certain to become confused and indeterminate when your
imagination allows two or more different power levels at the same place at
the same time. For example: the so called forward and reflected power
levels.

Imagination is assisted by the existence of meters which claim to measure
these imaginary forward and reflected powers. Actually they do nothing of
the sort. They even purport to make measurements on non-existent
transmission lines.

Reflected volts - yes!
Reflected current - yes!
Reflected power - NO!

(PS : You can't deal with reflections without involving Distance, Velocity,
Place and Time.)
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Reg.