With Vue 3 we're introducing tree-shaking of individual Vue features which will get rid of unwanted

The "production" build will ship with the stuff that particular project uses. That means both what they use in their codebase and what Vue uses internally to handle that code.

But there also has to be a way for Vue to understand what the user wants to be in the bundle. This is easier for the users who use the new syntax, where the individual features are explicitly imported.