I know I can "fix" this by calling reader.Update( ) or reader.UpdateWholeExtent( ); before engaging the whole pipeline by the viewer, however this is a simplified case of a whole set of big images for which I would not have the memory to hold them all in memory before clipping. And I know I would have to call ClipDataOn() for it to actually easy memory use, but I left it away for simplicity of the minimal use. Also calling clip.Update( ) makes an instance crash (segfault) before the viewer is even setup.
Below sample works with 6.3.0 tough. Identical C++ control application has the same effect.