This is really weird. When you go to the later time step with the larger extent, the Information tab is correctly reporting the changed extent and the data are correctly rescaled in the view, but for some reason it is only loading the smaller extent of the data. That is, at the later time step it should be loading a 961x1x321 array, but it instead is just loading a 481x1x161 array.
This looks like it might be a bug with the VTK pipeline. I think either the pipeline at the reader is not updating the whole extent during the request information phase or the update extent is not being updated at the bottom of the pipeline during the request update extent phase.
@utkarsh.ayachit, do you want to take a look at this?