Single click in system tray option on Preferences > Login page actually requires restart to be effective. Need to add a note as with other options requiring restart.
It seems that only some settings are not applied without restart. One click roster window opening is one of them (that i have found). Maybe it always was this way for this setting. Not sure if it needs a restart. If so, it should show a dialog and suggest restarting. Or at least have (requires restart) hint near it.
Changed issue as this is not happening with all options and only one option seems to be affected.