In the LWC documentation for debug mode it states (emphasis mine):
By default, the framework runs in production mode. This mode is optimized for performance. Framework code is optimized and “minified” to reduce the size of the JavaScript code
The docs seem to imply that there is more to the optimization beyond just minification. What kind of optimization are we talking about?
The closest I've found is in the section on bundling in the documentation for the LWC compiler which says that:
The final phase of the compilation pipeline is bundling. During bundling, Rollup will ‘statically analyze and optimize the code you are importing, and will exclude anything that isn't actually used. This allows you to build on top of existing tools and modules without adding extra dependencies or bloating the size of your project’. The end result of the bundler is a single javascript file in a specified format - ‘amd’ by default.
Is that the kind of optimization that the LWC docs are referring to?