I am not sure how exactly it will work. Even if the battalion had their original 13 scholarships and they had 30 applicants, it is still a question of how they communicate to the Army selection board which 13 applicants they want. Do they only recommend X number via the interview process or do they recommend everybody they want and just wait for the board to determine who will get the scholarships? What happens if the unit is assigned only 6 (or 13) and the board awards 10, does the unit pick which 6 they want?
Obviously I don't have the answers. It is possible that the call was just a "gut check" to see if my daughter was really interested and to make her feel special by being one of the six, but I honestly don't know for sure. I will say that I've now heard from a number of different people that the Army is reducing the total number of scholarships. I don't think their need for officers has decreased, so it must either be that they have found another way to supply those officers, or their budget has been reduced for some unexplained other reason.
I pretty certain the batallions can pull the full files for each candidate who listed them in their top schools. They can look at the score and know who they will be asked for a or first. Cadet Command does give veto power over offering a scholarship in a specific Battallion to the PMS there, as they will usually check with admissions if there is a question of whether or not the applicant will be admitted.
If the Batallion has 6 scholarship to give and they rank their favorite candidates (not necessarily the ones with the highest score, but the ones they feel will accept and be the type of cadet they want). If only 4 of them on their top list are in the first board, they will veto others, so as to leave the other 2 slots open for subsequent boards, when their candidates get their offers.
This would not be difficult to engineer at all and would be consistent with their checking the applicants intent of accepting, if they feel that the next board will be where they finish filling their allotment.