Keith Dysart wrote:
So I am summing the instantaneous flows for the two contributors of
energy.

An invalid thing to do when interference is present.
Reference EE-201 to find out when and why

[V1(t)^2 + V2(t)^2] is NOT equal to [V1(t) + V2(t)]^2.

The whole premise and assertion that the dissipation
in the source resistor is equal to 50w plus the
reflected power is based on the condition that

(V1^2 + V2^2) is equal to (V1 + V2)^2

Since you did NOT satisfy that condition, it
logically follows that the assertion would not
apply unless that necessary condition is met.

Please get back to us when you meet the above
condition. In attempting to do so, you will
realize why Eugene Hecht said that instantaneous
power is "of limited utility".
--
73, Cecil http://www.w5dxp.com