Remember, it took them 2 weeks to sort out the TI/SA bug comp, and that's when everyone receive the SAME comp (which they shouldn't, but that's neither here nor there). Seeing as everyone would be receiving different amount here, the workload might be quite a bit higher. (Also, they have to actually dig their database instead of relying on screenshots. They should have digged database for the TI one too, but that's also not relevant)
Now, they probably could issue the comp to people as they go, but that might be unfair as the earliest batch might be 2 weeks from the latest, and you saw what happens when some people receive comp and others don't, people will repeatedly complain and contact them in fear of being forgotten. So they probably want to avoid that and wish to compile a full list of player to compensate before giving out anything.
They probably need to form a plan of action on how to actually send them out as well, as it's probably the first time they had to send different stuff to a large number of different people. Again, I believe they would want to minimize the time difference between when the first one is sent out compared to the last.
So in the end, this might be the slowest comp to roll out ever, because it is the most complex one they have ever had to work on.