It's a new thing to try: you fly what you register for. That way, people know exactly what they are getting and with whom they will be flying. There is less flexibility for the CO, but on the other hand, in real WWII, groups and squadron CO's got the people HQ sent them and made it happen with the guys they got. So, you could think of this as an added bit of realism.
The lack of names at the beginning was a bug in the registration system as a result of a total redo of the whole ahevents.org site a little prior to this. It wasn't intentional, and it was fixed the next day.
We try new things in scenarios from time to time, to see what people think and to see how it goes. I figured that the majority of players would like it this way better, flying what they register for and knowing whom they will be flying with. It makes it possible for people to get what they want (if they register early enough) and for squad mates to make sure they are flying together (again, if they register early enough). But we'll see what people think. This one perhaps isn't the best test of the idea because of the bug in the beginning, though.