Cache asset via freshness in Angular 6 Service Worker

I'm trying to integrate the Angular Service Worker into a existing project. If I understood it correctly there are two cases how data gets cached in Angular SW. It is possible to prefetch or lazyupdate the asset data and to cache specific API calls and other XHR requests.

What I'm trying to achieve is to load an specific asset first via network, if the request runs into a timeout or is not accessible it will be served via the cache. Just like the freshness strategy when caching API calls. But it seems that there's no possible way to configure such a freshness loading mechanism for a JS file which is loaded as an asset in the Angular project. I've setup an example Project for testing: https://github.com/philipp-schaerer-lambdait/angular-service-worker-test

The following example is a standard Angular App and does not contain the actual project I'm working with but shows the elements I'd like to cache, the structure looks like this:

\_ Angular root  
 |_ src/
   |_ index.html <----------- links to excluded_asset.js
   |_ app/
   |_ assets/
     |_ excluded_asset.js <-- this one is excluded in ngsw-config.json
     |_ included_asset.js
     |_ ...

Here the relevant configurations:

ngsw-config.json

{
    "index": "/index.html",
    "assetGroups": [
        {
            "name": "app",
            "installMode": "prefetch",
            "resources": {
                "files": ["/favicon.ico", "/index.html", "/*.css", "/*.js"]
            }
        },
        {
            "name": "assets",
            "installMode": "lazy",
            "updateMode": "prefetch",
            "resources": {
                "files": ["/assets/**", "!/assets/excluded_asset.js"]
            }
        }
    ]
}

Is it possible to achieve a caching behavior like the freshness strategy by using the installMode and updateMode for the assets?

I've tried to exclude it from the asset cache and it was loaded via network but obviously won't be delivered by the service worker after going offline.

After that I've tried to include it again via dataGroups and setting the strategy to freshness but it seems that the asset won't get cached again once it is excluded from the asset configuration. Also I don't think that the dataGroups settings can be used for this file.

"dataGroups": [
    {
        "name": "config",
        "urls": ["assets/excluded_asset.js"],
        "cacheConfig": {
            "maxSize": 10,
            "maxAge": "1d",
            "timeout": "100",
            "strategy": "freshness"
        }
    }
}

Did I miss something or is there no way to cache an asset via the freshness strategy? It would be preferable not to move the file or to change how the file is being requested.

EDIT

I tried to move it outside the cached assets directories and include it with the dataGroups setting, didn't work either.

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