I’ve always heard that the nib was meant to help you gauge when to stop your pull stroke and start your push stroke so that you use the whole saw and don’t wear the teeth unevenly. Is this not the case?

Well that certainly would make more sense! I’m a cold weather person myself, but shorts in -5F is a bit much for me.

Christmas Day in 1983 was a record low for Chicago.

https://www.youtube.com/watch?v=WpT0vG56ADM

https://www.wunderground.com/history/daily/us/il/chicago/KMDW/date/1983-12-25

I’m not from the area, so I’m unsure if there are severe micro-climates in or around Chicago. Maybe, even, you and your neighbor are acclimated to very cold weather conditions. It’s irrelevant either way, as we would all be better served by not conflating weather with climate, which OP’s post is also doing.