This version wouldn't have an Nginx config to send all the URLs to the same frontend.

So, if you use React router with "new" routes (/users/john/items instead of /#users/john/items), when you open that URL (not by navigating in your app, but by copy-pasting the URL), the web server (Nginx) will show a 404 error, instead of sending your React frontend (your index.html) and letting the router handle what to render in that URL.

You can still do the Dockerfile by hand, but you would need to include the Nginx config yourself.