RP wrote:

Conventional Heat Pumps get an average COP of 2 to 1...

Thus if the overnight (set back) runtime is reduced by an amount of time
that is twice the recovery time with heat strips enabled), then energy
is saved over not setting back...

Thus? :-)

Thus, yes, at some higher COP and/or warmer climate the trend will reverse.
That's why I said in summary that economy depends upon the system

I don't quite see a "thus" there. Would you further explain your logic?

Would you agree that night setbacks always save energy if the heat strips are
switched off, even though that may require longer reheating after the setback?

Nick