Well, that's about 33µA@3V, one can power many kinds of low-power stuff with that. Watches of course, even pretty advanced ones, all sorts of sensors. We now have many low-power MCUs that can run at honorable speeds with this kind of current.
If the claim of 50 years is real, meaning continuous delivery of 100µW for 50 years, that would be nearly 15Ah, which is gigantic relative to the size of this battery. Sure the amount of power it can deliver is limited, and the technology wouldn't scale all that well as Dave pointed out, but that's still pretty impressive. Would this even run for 50 years straight without failing though? Allow me to have some doubts.
And of course, as I said before, I'm curious to see when authorities would allow any kind of "nuclear" battery outside of very niche and heavily regulated fields, at least outside of China. Let me know when that happens.