Unclear purpose of StoreResponse.NoNewData

What does it mean when a Store emits StoreResponse.NoNewData?
Documentation says only the following:

/**
     * No new data event dispatched by Store to signal the [Fetcher] returned no data (i.e the
     * returned [kotlinx.coroutines.Flow], when collected, was empty).
     */

How is it possible for a Fetcher not to return data?
Taking an example from the readme:

StoreBuilder
    .from(
        fetcher = Fetcher.of { api.fetchSubreddit(it, "10").data.children.map(::toPosts) },
        sourceOfTruth = SourceOfTruth.of(
            reader = db.postDao()::loadPosts,
            writer = db.postDao()::insertPosts,
            delete = db.postDao()::clearFeed,
            deleteAll = db.postDao()::clearAllFeeds
        )
    ).build()

when would this Store return a StoreResponse.NoNewData?