Tabbed Panels/Tabs via Resource Strings

Is it not possible to create Tabbed Panels and Tabs using a resource string?

On both CS5 and CS6 this works:

var win = new Window ("dialog","Tab Test");

win.matchtabs=win.add("tabbedpanel");

win.matchtabs.taba=win.matchtabs.add("tab",undefined,"Match #1");
win.matchtabs.tabb=win.matchtabs.add("tab",undefined,"Match #2");

win.show();

but this:

var res= "dialog { matchtabs: TabbedPanel { taba: Tab { text: 'Match #1' }, tabb: Tab { text: 'Match #2' } } }";

var win = new Window (res,"Tab Test");

win.show();

fails with "Error 19: ... TabbedPanel is not an object" , again both on CS5 and CS6.

Thanks for any insight.