But, to restate my previous comment: if you have a natural gas furnace and a GPU, but no heat pump, and are deciding which to use for heat, it doesn't matter how efficient the heat pump you don't have is.
If you own your own home and have the capital to get a heat pump, great, do it. But a lot of people rent. They can't just swap out their furnace for a heat pump.
As an extra benefit the heat pumps have lower maintenance, risk.
Ahh, now I see where there might be confusion. Heat pumps that operate on electricity are increasingly common in the US. Most of them are air-to-air, but some are ground-source. What I'm claiming are rare-to-non-existent are residential heat pumps that operate directly off of natural gas, using an ammonia absorption process, with no electricity involved.
Arguably 'freemint' was saying that it's more efficient to generate electricity centrally using natural gas and then distribute this electricity to power heat pumps than to burn natural gas for heat at each site. Yes, likely. My surprise was that I thought he was claiming that non-electric natural gas powered heat pumps were currently available to residential consumers. I knew this style exists (see the link I gave above) but I've never seen one in operation.
We should evaluate things against what the actual, real world alternative would be, not just against the best possible world.
(That said, I should acknowledge that a large part of that electricity comes from burning natural gas at an efficiency loss, so resistive heating is still worse than the natural gas furnace.)