Not necessarily. You will see people being appt to the SA before the nom process is completed. In areas like NY and VA they do not like giving out multiple noms to spread the wealth, since only 1 nom is needed to be appt. If a kid has an LOA and a Pres. they never apply for the MOC since they will come in that way. There are also kids that never get an MOC even though they applied for one, so their name is not even on the list, however, the #2 on the list has Pres, but never gets appt. because their WCS is lower. In theory you would believe that the number 2 would be higher since they have an MOC nom and the other child does not, but theory and reality rarely ever are the same. The SA can also bring someone in on a VP or ROTC before touching the Pres. noms. They could even use the Supe before the Presidential. In the end they want the highest WCS recipients to make it, so they move the candidates around to get the optimal class.
It is possible that a candidate could have a Pres, VP, 3, MOCs and a ROTC nom. That means they could slide that person in 5 different ways before they hit the Pres. appt. This is a puzzle they are making and they have no idea what the picture will look like until the last few pieces. This is also why I have stated you might have your packet in and meet the board in Oct., but not receive an appt until the mass mailing in Mar. That is also why you need a back up plan. The SA's are in a way rolling, but it is unique. With Pres. they can start appointing without the entire slate, with MOCS they cannot. Again why they may give you an appt earlier. These are cases where they know from historical data that you will get in. For ex. your WCS is higher than the top 25% of last yrs pres., thus, they expect that your WCS with a Pres will win and give it to you in Oct. Then there are those who are at the tail end of previous yrs WCS, so they wait until Mar. to see if they can get you in.