Pima is quite correct. Assuming you have your application 100% complete; you now have a nomination; and they've even figured out your weighted candidate score; how can they CHOOSE you to receive an appointment, when the rest of the individuals in your district/state/and nationally; have until the end of January to complete their application? In other words, they can't compare YOUR WCS to someone who doesn't have their score yet. See, you can get the nomination prior to finishing the application. That is quite common. If it wasn't, then the cutoff for finishing the application would probably be in december.
Now; there is of course exceptions to every rule and caveats. In this case, IF, and I say IF SPARINGLY, the senator or representative who gave you your nomination uses the "PRINCIPAL" method; whereby they declare YOU as their #1 PRINCIPAL Nominee; then the academy can most definitely give you your appointment early. Because if you're the PRINCIPAL, then the academy has NO CHOICE WHATSOEVER in you getting an appointment. (Assuming you are 100% qualified). But even then, they pay choose to wait. Because, if you have more than 1 nomination, even though one is a principal, they can guarantee you the appointment, but use one your other nominations so they can get someone from the slate you were the principal on to get another person in. The nomination process is very complicated, but there is a method to the madness. So if you have a principal nomination, (Which is not the norm for most MOC's), then the academy wouldn't need to wait to compare your score to others. But without a principal, they sort of can't compare you until everyone has their applications completed and have their scores.