We have 2 possibility of dealing with Core language packs:

One would be indeed to use the folder trick and would fit very well people using crowdin for example where the packs will anyway contain all ini files and are created automatically (almost).

The other is to keep the install.xml as is because it is a very easy way for TTs not using crowdin to know by diff what has been added or deleted from core.

Com_localise creates the install.xml automatically and one would not have to bother with that tool.

Back in the days I was not using Crowdin (or even way back when using Transifex) I always used a Diff tool to know if there was new files added by comparing folders. The XML list brings nothing useful for diff tools.
So:

• Teams using Crowdin do not need XML list and will work way better without a file list on the XML file
• Teams using "com_localize" tool do not need xml file (in the core) because it creates a new one for them
• Any other teams (is there any left?) will not gain nothing having 2 more files to look for diff files as they can diff the folders where the actual changes are done.
• Core developers do not need to maintain a list of files in the XML file (less work for them too)

So... there is no need for a file list on the language XML file, and those lines should be removed!

Just so there is some code to show: staging...Bakual:SimplifyLanguageInstallXml is what is talked about here.
I tested it with the german pack but want to test with some more complex languages if it would work there as well.

Created the PR.
Languages that have additional files (eg media files like Persian does) will need an adapted install.xml where the language files are moved into a subfolder so the media files aren't copied into the language folder as well. But other than those, it should work fine.

Closing this issue as we have a PR where the discussion can proceed ?