They're probably going to have a small amount of destination servers, but they're transferring into them one origin server at a time in order to monitor the population.
Example: let's say there's 20 destination servers, but 100 origin servers. Ideally, you'd have 5 origin servers going into one destination server. But you want to monitor the traffic to see if maybe one server needs 6 and another needs four to get the best population balance.
Unfortunately, in order to do this properly, it requires time for the developers, and (god forbid) patience from the community.