`chrome.downloads.search` is missing file results

Question

In the context of a Chrome extension, I want to map some local downloaded files to in-storage data.

I'm having trouble understanding why a file that is clearly in the desired folder according to my OS would not be detected by chrome.downloads.search?

❯ ls ~/Downloads/PaperMemoryStore/*2101*
/Users/victor/Downloads/PaperMemoryStore/2101.02464.pdf

const allfiles = await new Promise((resolve) => {
    chrome.downloads.search(
        { filenameRegex: "PaperMemoryStore/.*" }, 
        (p) => resolve(p))
    )
});
allfiles.filter(f => f.filename.includes("2101")) // [] <- empty filter

I understand why allfiles may have more results than what the filesystem shows (because of DownloadItem.state for instance) but not why it would show fewer.

Is it possible that chrome.downloads.search would not return files that have not been downloaded but just put in a folder? I could not find any such information in the docs.

Scenario:

1. I downloaded a pdf (2101.02464.pdf)
2. Which I copy-pasted in a sub-folder of Downloads/ (PaperMemoryStore)
3. I'm running Brave Version 1.36.122 Chromium: 99.0.4844.88 (Build officiel) (x86_64)