Notice that Tilson refuses to comment on any details of his short position. He even made the remark that it is a relatively small position. Then why bother to even disclose it? Unless he is starting to worry about the beginning of a short covering rally. Ackman is probably his good buddy and asked him to make some remarks to the media to get more support for his short position.
yeah it was something like that, he reversed his short after doing a huge amount of homework and publicizing his thesis I believe . . . then he reversed and announced he was long and got hit. Or something like that, going back a few years and I did not look anything up before posting - relying on my failing memory! lol . . .