The author says almost exactly the same thing at the end. Maybe it should have been at the beginning.

When you have to run resistive heaters the electrical usage skyrockets and makes a heat pump system vastly more expensive to operate.

More expensive than a heat pump without a backup/additional electrical resistance heater. Not more expensive than an electrical resistance heater on its own.

That’s what’s so strange about this, in most cases a heat pump would be replacing a non-reversible AC and an electrical resistance heater or gas-fueled furnace. And in nearly every case, even with the need for a backup/additional resistance heater, you’re still saving money. And it’s not like any of this is new technology, it just took forever for it to become popular in the US.