When you reference a .js framework or library from your ASP.NET application, it makes sense to use the development version when you’re working on your own machine.
Referencing the development versions brings more useful error messages and integration with the React Developer tools.
But, you wouldn’t want to use these in production for performance reasons.
When you run the site in production, you’d want to reference the minified production versions of the React scripts.
Source: Different js scripts for different ASP.NET core environments· jonhilton.net – Making sense of .NET