I think there might be something to this theory. I know a few past SSHRC-winners in my program who got a rejection letter from OGS only to get SSHRC a couple of weeks later. By the way, these students also told me that they got their SSHRC letter last year on April 24th so we're not necessarily "late" yet - though certainly past "mid-April."
But if this rumour about late-April/early-May is true, my suspicion is that Harper's "addition" to the system has created some complications requiring more scrutiny of the process (e.g., determining what is "business-related"). I've heard that there is somewhat of a revolt amongst some of the panelists who are stretching the definition of 'business-related' as wide as possible to undermine Harper's intention.
Nonetheless, I'm about to blow my head off.
(It is 1:30am and my wife just poked her head in my office trying to figure out why I was still up. "Oh, you know, just reading through SSHRC chatrooms...do you mind?")