I can confidently say that no it will not “intelligently use the LAN” when you’re on the same network - I don’t know of any service that will… unless Plex/Plexamp somehow does this?
The solution is as someone else said - use a DNS Server to forward it in your LAN to the internal IP. If you’re unsure how to do this, just search how to setup a Hairpin NAT for the router you own. I can confirm that once you set this up, it will work seamlessly with both Finamp and Jellyfin.
So the author of the blog post that the article is based off of actually interacted with some comments over on Hacker News and there were some pretty interesting revelations - such as his resume having Vibecoding as the first skill listed on it and living/looking for jobs on the East Coast with a website sounding like he’s on the West Coast among other things.
I guess the media saw his blog post as a quick means of driving clicks through a clickbait headline. That’s not to say that the market isn’t hot trash at the moment, but I personally doubt Engineers are being replaced by AI.