This is probably a good example of the opposite. It would be a mistake to design for the fleetingly rare case. If you’re dealing with a handful of extensions, a json file that’s rewritten is fine.

But the software already has multiple database systems built in. There's not exactly overhead to use what plumbing is already there, instead of writing to disk.

In an ideal world, software with 100 million users would be optimised for energy usage. It all adds up. This does pale in comparison to everything else, though.