Currency misunderstanding - not buying it. If that was a currency misinterpretation, then you would have 4.2 million volume in Canada and not in the US. The dumping was triggered in the US and trickled north of the border. In fact almost all was executed on ARCA and BATS exchanges not Nasdaq. Have no idea what those are but google says they are global exchanges possibly with European affiliation. Therefore I had another theory.
I tried to go back to the conference call to refresh my memory if the 8.49M shares that were to form the payment to the hedge fund Cinven were already issued to them. The CC is no longer available. Is it possible that if Cinven is in possession, they just decided to dump? They are a hedge fund after all and have the means. Goldman's shares have not settled yet, so who else could create volume in the millions?
Thompson did mention in that CC that Cinven would dispose of those shares in an orderly manner in early 2016, but maybe they got Pee'd off with the Goldman deal and said F this and dumped. Who else?