In the past I've certainly seen that, but more and more I see all the language files being installed. You never know when someone is going to change their language, add another one, or add a new user.
Firefox certainly did this [Firefox release engineering](https://aosabook.org/en/v2/ffreleng.html) but at one point, having >100 almost identical executables (with the text swap out) for each version would eventually got on some nerves.
But aren't those things rare enough that it's better to have people doing them rerun the installer, than to take up extra disk space for everyone that most people will never use?
No. Language resources are part of the app bundle, which means they are part of the bundle’s code signature. Removing or altering them breaks the signature.