cwhs
This is by far the weirdest process I've ever seen. Waitlists in waves? Why?? My file's been sitting there for the past three months with the interview completed and all, there's no way that they haven't made a decision on it yet. So what's the hold up?
To be fair, if you visit threads of other schools that release every decision on a single day, you'd see weeks of angst laden posts like "Adcom has probably already reviewed my file and made a decision... why can't they just tell me already!"
If I had to make SWAG, I'd say that waitlists, and other "on the fence" candidates, have to wait until the end of the process, because Adcom won't be able to make a final review and final decision on those files until they've reviewed the entire class and know exactly where they're drawing the line, so to speak. That could be one explanation for this odd pattern. But who knows.
In the tradeoff between one decision date (slower but less stressful) and a rolling window (potentially faster but more stressful) Adcom has to make a tough call. Kellogg just makes that tradeoff differently than other schools. But it's not an illogical, indefensible process.