ImageView does not support Polygon sprite frames.
Scale9Sprite is used as the renderer but instead of calling setScale9Enabled(false), setRenderType(SIMPLE) is used instead. This means that Polygon information is ignored as _scale9Enabled stays true by default and the 9slice geometry is used instead.
Could ImageView not make use of Scale9Sprite::setScale9Enabled()? Or perhaps a third RenderingType could be designated? - SPRITE?