My brother has a heat pump in a super efficient house.At -20C it doesn't produce any heat for the electricity it uses.
They certainly make less heat as temperatures drop below freezing. This is part of the specifications and design.
Luckily, modern equipment should deliver about twice as much heat as the electric consumed down at least -5 F. If that’s not enough heat for your brother then that was a design decision.
I would want a good secondary system in that climate!