The IAEA maintains the International Nuclear and Radiological Event Scale, under which a level 7 incident is one that requires the implementation of countermeasures to protect the public[1]. The details of those countermeasures and the scope of the accident is not significant - all that matters is that _some_ plan to counteract the effects of radiation was undertaken. The IAEA even cautions against using the scale as a means of comparison between facilities and incidents. In this context, the Chernobyl incident involved the release of 10x the radiation [2]. The effects on human and animal health also appear to be orders of magnitude different. So really, grouping the two incidents together is counterproductive. Doing so, to me, reflects a misunderstanding of the INES - one that I suspect is deliberate on Greenpeace's part.
1 - http://www-ns.iaea.org/tech-areas/emergency/ines.asp [2] - http://www.sciencedirect.com/science/article/pii/S0048969713... (2014, but I'm not aware of revised figures from the past two years)