I also just received the same increase to $2000 after expect $750. What's really funny is that I got it about four days after I forgot to make a payment (I paid 1 day late)! This was my 6th or 7th payment though, so it was after fulfilling step requirements I believe.
If it helps, I have both the platinum and the BS rewards card (hit $750 on that through step) that I have used to build credit credit. Basically, both cards started at $500 and I used both cards sparingly, never had a balance of more than $150 or so and always paid it in full upon the due date. I also made sure to use the cards at least minimally every month. I feel like there is a chance that because I had both cards and paid both on time and in full for over six months each, I received the increase. Good luck everyone!