Project Settings keeps appending {fileID: 0}

Forum users have reported that when using the new input system, an "{fileID: 0}" string keeps getting appended to the projectsettings.asset file:

https://forum.unity.com/threads/project-settings-keeps-appending-fileid-0.954147/ 

Although this was supposed to be fixed in:

https://issuetracker.unity3d.com/issues/projectsettings-dot-asset-is-checked-out-in-perforce-when-building-a-project-with-the-input-system-package-installed 

They are still reporting this issue, including in 2021.3 on WebGL, Windows, MacOS, and Linux. This needs investigating.

Here's a brief conversation about this in #devs-input: https://unity.slack.com/archives/C09Q7LYP9/p1660762430036649 

I'm unsure if this is a regression so I'm going to go with No. I'm making it a public ticket for users to track progress.