trying to shutdown + restart embedded webextensions without a restart

foo.js

// 1. This seems to work. Is it safe to use?
const { EmbeddedExtensionManager } = Cu.import("resource://gre/modules/LegacyExtensionsUtils.jsm");
const webext = EmbeddedExtensionManager.getEmbeddedExtensionFor({id: '[email protected]'});
webext.shutdown();
webext.started = false;
webext.startup(); // throws no errors, toolbar button reappears, messaging works

// 2. This doesn't work:
const webext = EmbeddedExtensionManager.getEmbeddedExtensionFor({id: '[email protected]'});
webext.shutdown();
EmbeddedExtensionManager.untrackEmbeddedExtension(webext);
const another = EmbeddedExtensionManager.getEmbeddedExtensionFor({id: '[email protected]'}).catch(err => console.log(err));
// fails with a Malformed URI Error because the resource URI wasn't specified

// 3. This also fails:
let pageshotAddon;
AddonManager.getAddonById('[email protected]', addon => { pageshotAddon = addon; });
const third = EmbeddedExtensionManager.getEmbeddedExtensionFor({
  id: '[email protected]',
  resourceURI: pageshotAddon.getResourceURI()
});
third.startup();
// fails with FILE_NOT_FOUND error trying to load the manifest from the wrong location:
// $PROFILE/extensions/webextension/manifest.json, rather than from the webextension inside pageshot