aristotle - 2:03 pm on Jun 9, 2012 (gmt 0)
As far as I know, link devaluation was not a direct part of Penguin - even though it occurred around the same time. Penguin was a true penalty against specific sites, not just an ignoring of certain links.
I agree that two different things happened, but I think they occurred either simultaneously or at least on the same day. ( I believe it was April 24.) My reasoning is as follows:
1. On my two sites that were affected, most of the pages only fell 1-3 positions in the rankings for their main keyword. A few even held onto the number 1 position. These pages have moved very little since then.
2. However, some of the pages on these two sites had bigger initial drops, at least 20 positions, and these pages have dropped even more since that initial drop.
So the pages in category 1, which fell only slightly, appear to have been hurt by a massive link devaluation, but weren't "penalized", at least not for their main keyword. But the pages in category 2, which fell much further, apparently were penalized for their main keyword.
Since both categories of pages were initially affected on the same day (April 24), I think that the link devaluation and the Penguin implementation both occurred on that day, and possibly even simultaneously.