Fascinating, thanks for explaining! I had assumed it was just that capacitors were easier to get hold of than batteries, and that the author was just putting up

Fascinating, thanks for explaining! I had assumed it was just that capacitors were easier to get hold of than batteries, and that the author was just putting up with a reduced "battery" life as a result. It makes sense to replace with capacitors if they're just using it for always-powered static applications -- probably with much lower fire risk to boot.