This is a news article, not a study, which would've more likely used Kelvin, which would be still 12 degrees. It's for everyday people, which almost all of which use Celsius to measure temperature. People outside of the few countries who use Fahrenheit don't get confused about it because it's literally the only measurement they use in their life. If you travel outside the US you will find that no one adds Fahrenheit conversations anywhere and that pretty much all temperatures are listed in Celsius.