They booked the dates I wanted up to a point about a month from where the bookings are open (~300 days ahead). Beyond that they used that last 30 days and booked the remaining legs so that each leg had a bookable date and the "trip finished" 330 days from the day that I made my booking. The agent said to be that the ticket "has to work". So these are just bookings that require a date change which she assured me was not an issue (contrast with Qantas who said that each of those would be a $125 change fee). On my ticket, every leg has a date and a flights for that date.