Spoke with a representative today.
The 0% down and no PMI only applies to the 5/1, 7/1, and 10/1 ARM mortgages.
My basic understanding of ARM is that the interest rate is fixed for a period of 5, 7, or 10 years, then the rate can be changed once per year depending on an index rate.
Not sure how much sense this makes for a first time buyer to use vs. a 15 or 30 year fixed-rate mortgage, especally considering current low rates.