If we’re being honest with ourselves, the real reason that we use windchill values when we’re talking about the weather is for dramatic effect.
Windchill is a scientific measurement of how quickly warmth is shed, so how it relates to you and I and how it feels cross Portage and main (if we could) isn’t really what it’s about.
That said, it is a thing when it comes to how the temperature feels. If you step outside naked at -20 with no windchill, not only will the neighbours call the PoPo (again?!), but it will feel way different, and you’ll live a lot longer than you would if you did it at -20 with a windchill equivalent of -40.
Apart from that, who really knows anything about it?