Where does it say it uses script tags for input? The quote you mention says CommonJS/AMD. CommonJS is the de-facto standard these days. Typically, people write in ES6 imports, which then gets transpiled to CommonJS anyway.

It accepts AMD as an option, but honestly, I've been using webpack for about a month and I haven't come across a single library that recommends using AMD. It's just there as an option for those who need it. Most of the world has moved on from AMD due to its issues, so I can't really see your point.