We added a reference to the treeview control (from 2013 Q2 SP1): http://www.telerik.com/products/aspnet-ajax/whats-new/release-history/q2-2013-sp1-version-2013-2-717.aspx
I'm not really sure why this feature is an "idea" or needs to be "considered". A tree-like control without server-side access to a nodes collection seems to be missing pretty standard functionality. I doubt Telerik would be asking the public if they think their treeview control should provide server side access to nodes. This is no different.