At those temperatures that pump works at COP of 1. Basically it just switches on the resistive heating element it has for this case. What is being talked about

At those temperatures that pump works at COP of 1. Basically it just switches on the resistive heating element it has for this case. What is being talked about here is having one that actually works as a heat pump at those temperatures instead of a resistive element. Though if you live in a place where such cold days only happen a few days per year tops this is just fine.