Is a primary nomination the same as principal? If not, can you explain the difference.
Where are you hearing the word "PRIMARY"? You don't give enough info. MOC's have the choice of providing their list of 10 nominees one of 3 ways.
1. Principal (First person on the list) and the other 9 names simply listed and the academy can rank those 9.
2. All 10 names Ranked, with the first being their "Principal" and the other 9 all ranked according to the MOC's decisions.
3. All 10 names simply on the list, no priority, and the academy ranks them.
The 9 in #1 and the 10 in #3 above is commonly known as "COMPETITIVE". In other words, the academy scores each candidate and ranks them against each other. The difference with the "PRINCIPAL" in #1 and #2, is that the MOC has specifically said, my #1 "PRINCIPAL" nominee is "John Smith/Jane Doe". Once the MOC does that, the academy has ABSOLUTELY NO CHOICE in the matter. They MUST give an appointment to that "PRINCIPAL" nominee. ASSUMING: The MOC has an opening, (Which they probably do or they wouldn't have submitted a slate of nominees), AND the Principal nominee MUST BE 100% Complete with their application AND 100% qualified.
In other words, the PRINCIPAL nominee, if that's how the MOC listed them, could have the lowest scores of all 10 nominees on the MOC's list, and the academy STILL MUST GIVE THEM THE APPOINTMENT if they are qualified.
2 things. Very few MOC's use the Principal method. They normally use #3 above. Give 10 names and let the academy choose. The other thing is; if the MOC does use the Principal method, they know what they're doing. They aren't going to give the Principal to the lowest scored person on their slate. The person who receives a Principal, most always deserves it.
As for PRIMARY; I have no idea what you're talking about, unless you're trying to use the two words interchangeably.