I think they are taking additional precaution to open the flight envelop, may be any mishap at this stage can seriously put things backward. So it means they will open the full flight envelop between IOC and FOC only? I think they will test the full AOA only after testing most of the other subcomponents fully.
Also testing first time an aircraft is most difficult thing to do and time consuming. Since we don't have any previous data to guide, seems that's why things are moving very slowly. I think the test data generated by LCA will reduced the testing time a lot for the future jets. No one will ever share the testing data with us, so we will have to to get it by ourselves only.