The Sunny 16 rule doesn't state that it applies to all situations at all times. It's concerns average conditions. So, the whole "not in my neck of the woods" exception argument is kind of superfluous.
One problem with rules of thumb, Kodaks Exposure Guide, or the Black Cat Guide is that they don't give any reasoning. The ANSI Exposure Guide gives charts showing the change of light conditions at different latitudes, at different times for day, and at different times of year. It also offers the variations do to weather conditions. It's said that if you use that guide correctly and your light meter disagrees with it, your light meter is wrong.
Most Sunny 16 discussions just dance around the concept, which at its heart is exposure theory, instead of delving into what it's about and where it comes from. Let's not forget, Sunny 16 rule has more assumptions to it than just Sunny. What is considered the average daylight illuminance? At what solar altitude? Under what sun, subject, camera interrelationship? What is the intended camera illuminance? Where on the film's curve should exposure fall? Among other questions.