Ah! But this chip only has a sub-uA sleep mode. So it will have the said decades battery life if it sleeps most of the time, which might be true in the cases of some kind of IoT application, but not if it's actually running often.
Meet marketing. I will personally buy pizza for one week to any marketing department that, when announcing a new product, publishes figures that are actually useful.
Oh look, we just launched a MCU with a power consumption so low that you can keep it powered for twenty years. As long as you don't do anything with it. Of course, every other figure that would make this one useful (such as per-module current consumption, time to sleep) is missing.
It's especially funny when everyone claims they have "the best" or "state of the art" consumption, but when you factor in everything else it turns out they're pretty much within the noise figure of the current state of affairs.
In my whole engineering career, I'm yet to see a press release or a market launch that isn't full of bullshit. Just hand me the bloody datasheet and give me a break, folks.
