I don't know about Washington, but myself and several of my colleagues had to deal with the Chicago passport agency. There they do not always provide same passport issuance and some people get their passports the next day and some others get their passports two days after the appointment. It all seems to depend on how far from the appointment date the travel date is. I was told that if the travel date is more than a week but less than two weeks from appointment days, the passport is ready two business days after the appointment. For people with less that a week to their travel date, either same day or next day service is provided. In my case I had an appointment on Friday and my ticket was for the following Monday (in 3 days from the appointment) and I got my passport on the appointment date. But two of my colleagues had to wait two business days for their passports.
I am not sure if the Washington passport agency uses the same method as the Chicago one, but if they do, then the actual travel date you put in your passport application is important and will make a difference on how quickly the passport will be ready.