What's the point of bundling libraries? Bundling applications, ok, but libraries? Unless they are dynamically imported straight into browser, then it doesn't matter for any use case I can figure.
For node applications, startup time is impacted by IO a many files is less nice for IO wait times. So bundling does make a material impact for non-bundled backend applications and large libraries. I do agree, most impact is had when using bundling at a moment closer to the deployment.