alt Hacker NewsWell, the problem an index over multiple documents solves for is also not present in the application presented by the article. The plan for an individual trip (or even a lifetime of trips for most people) is not going to exceed a size that can be handled and indexed on the client.
You're right, the approach totally works for PKM apps with less than, say, 1 person*year of data, which is literally the first sentence I wrote at the top of this thread. (But – there are a lot of architectures that work with casual datasets! Like, store everything in a text file. Or fork bitcoin and run a full node on device, for that matter. What are we trying to accomplish here?)