Double tall grass now shows a sunflower.

Confirmed, but only for player placed tall grass. Breaking tall grass created by world generation still shows the peony.

EDIT: I have tested this issue and it seems that it was newly introduced in 15w34c; in versions before that, breaking double tallgrass always showed a peony. Not sure what changed then, as there seem to be no bugfixes or features listed on the wiki that have anything to do with blocks.