Browser.storage.StorageArea.onChanged is undefined

Steps to reproduce:

In a WebExtension, I am trying to utilize browser.storage.StorageArea.onChanged in a background script, but I am coming up with browser.storage.local.onChanged being undefined.

This example code fails:

browser.storage.local.onChanged.addListener((change) => console.log(change));

Here is a barebones repository that can be used to demonstrate this exception.

Expected behavior:

browser.storage.StorageArea.onChanged.addListener should succeed like it does in Firefox and Chrome extensions.

Orion, OS version; hardware type:

Orion: Version 0.99.124.4.1-beta (WebKit 616.1.14.11.1)
OS Version: macOS 13.4 (22F66)
Hardware type: MacBook Pro (Apple M1 Pro)