The CallbackPanel from Syncfusion Studio 4.1.0.50 / Essential Tools was added to the comparison. This CallbackPanel allows AJAX callbacks similar to the Telerik r.a.d.callback framework. It seems that the Syncfusion framework utilizes the existing ASP.NET 2.0 client callback functionality to do the hidden postback in ASP.NET 2.0.
As with other commercial frameworks you have to buy the whole suite (in this case the "Essential Tools") which has many more controls included.