Remove dependend composer packages via replace?


I’ve found some posts in the web (like here or here, which is Magento related) that recommends to use composer’s replace in order to remove dependencies. They specify it like this:

"replace": {
    "magento/module-fedex": "*"

How does this work? Actually, it is a removal and not a replacement.

Is it a hack? I’m wondering also because I’d say if a package is required it is supposed to be an essential part and therefore cannot just be dropped since that may break the app.

Source: Composer php