In RCP, MenuDetectListener fires first, then menu creation (menuAboutToShow). In RAP, menu creation happens first, then MenuDetectListener.
This causes the menu to be created for the previous tab item instead of the current one, for the same reason it is not possible to block menu creation by setting "e.doit = false" in MenuDetectListener so tab menu appeaser for elements in tab together with tab menu.
Snippet attached.
eclipe-menu-snippet.zip