This isn't true. Unless you're roasting until it literally takes like only charcoal, like noticably darker than a 2nd wave French roast, caffeine doesn't really roast out. Caffeine also seems to be pretty significantly more soluble in darker roasts so between two cups brewed normally with the same mass of coffee, there will be more caffeine in the darker cup. They will have almost the same amount of caffeine if you do a cold brew process.
Darker roasts do burn off caffeine but it also makes the bean more soluble. Testing has concluded that in the end lighter and darker roast cups end up with generally the same caffeine concentration.
This is probably robusta coffee, which has 2x the caffeine compared to arabica.
No, I have a favorite brand of coffee that I buy, so I won't be trying this anytime soon. I had to look it up though, because I had a hard time believing it was a real thing.