Unfortunately at this time we have not planned any improvements of that particular feature of this example for the release that is scheduled for next week. What we have done however is complete revamp the service implementation and provided a comprehensive test suite to the example.
Rest assured that we have noted the request and will look further into improving this behaviour, you can actually do so on your own by playing around with the DescriptorExtensions class and the extensions methods in it. The format that the service can parse is regular Dynamic Linq expressions. You can find more information on that topic in this blog post.
I hope this proves to be helpful. Do let us know if you have further questions.
the Telerik team