Hi Liam,
I think your question is: Do I need the CLI to serve my universal app?
Did I get that right? The answer to that question is no. The CLI is a development tool, not meant for serving anything.
However, you do need a server that can render the universal part. The samples show a NodeJS express server sample. There are others available, My friend Maciej, wrote a couple of nice schematics to help you there too. Those are more geared towards "serverless". Also, the Firebase team has something that enables you to use their service to host a serverless app.
What server/language are you looking for?
Regards
Sander