It's semi-true even with modern systems and shouldn't be outright dismissed as "nonsense".
A normal person is scared of the prospect of losing heating when it's most needed. -15F accounts for many places in the US, but many others, not so much. Even New Jersey, which we don't think of as the frigid North, can theoretically drop below that number, and nobody wants "almost always" when it comes to life-giving heat in the coldest winter.
no, this is complete nonsense and should be dismissed as such.
People being "scared" is how north america ended up with vehicles the size of tanks. The vast majority of cold climate heat pumps work down to - 20 C in most cases and down to -30 with better models.
A normal person is scared of the prospect of losing heating when it's most needed. -15F accounts for many places in the US, but many others, not so much. Even New Jersey, which we don't think of as the frigid North, can theoretically drop below that number, and nobody wants "almost always" when it comes to life-giving heat in the coldest winter.