Are we certain that this is actually true in the sense that it's safe to do this?  The reason why we needed to run the update application in standard mode on OS X was because, when it spawned the game executable as a child process, that game executable was also run as root if the update application had been run as root, which resulted in a number of problems, including root being flagged as the owner of the save and config directories instead of the user, leading to bugs of the form of save files not being able to be created in the save directory as a result.  Given that OS X and Linux are both Unix-based, I would not be surprised if the same bug would prove to exist on Linux if we did things this way.  The reason why running the update application on Windows is OK is because admin mode in that OS is via an application-specific token, rather than a result of which user the OS thinks is running the application, so when it spawns a child application it isn't being run in admin mode.

Unless there's something known to be different between OS X and Linux in this area, I think it would be safer to have the UpdaterHelper on Linux to be run as root while the updating application itself is run as a standard user, same as how things function on OS X.