The effective preference used by the Eclipse IDE is the one under

org.eclipse.ui.ide, not the one in org.eclipse.ui. deprecated
IWorkbenchPreferenceConstants.PROJECT_OPEN_NEW_PERSPECTIVE no longer
influences current project-opening behaviour.

Author: elsazac

bundles/org.eclipse.ui/src/org/eclipse/ui/internal/UIPreferenceInitializer.java

@@ -52,10 +52,6 @@ public void initializeDefaultPreferences() {
 		node.put(IWorkbenchPreferenceConstants.OPEN_NEW_PERSPECTIVE,
 				IWorkbenchPreferenceConstants.OPEN_PERSPECTIVE_REPLACE);
 
-		// Deprecated but kept for backwards compatibility
-		node.put(IWorkbenchPreferenceConstants.PROJECT_OPEN_NEW_PERSPECTIVE,
-				IWorkbenchPreferenceConstants.OPEN_PERSPECTIVE_REPLACE);
-
 		// Although there is no longer any item on the preference pages
 		// for setting the linking preference, since it is now a per-part
 		// setting, it remains as a preference to allow product overrides of the