I felt like that’s more like a rhetorical device for shorthand-saying “one might expect a ten or twenty degree difference based on modern marketing”, and I’m annoyed the article didn’t say that because it’s a pretty good point delivered rather poorly.
It would be hilarious if they did find a 10 degree difference. “Old gear keeps you chilly but fine. Modern gear straight up kills you!”
A 20* swing in body temp would render you dead…