In my area, it is common for representatives from each school all in the same room asking questions of the candidate. The board does see that a student is applying to multiple SA because they provide that information as part of nomination application - which SA would you like to be considered for and rank them in order of your preference. It is common for a student to apply to multiple. Representatives from the candidate's top choice will generally begin the questioning of the candidate. When only applying to one, they ask why. When applying to multiple, they ask why. If applying to USNA but not USMMA, they ask why. Follow-up questions are spawned based on the candidate's response. If you want to fly, you can fly out of all schools - why just pick one? The answer is quite telling towards the candidate's research and understanding of what they are committing to. I was blown away by a student in a recent board who preferred one school because of their success record with getting students into a medical path after undergrad. She knew her stats (USNA had X, USMA had Y, and USAFA had Z in the class of XYZ) and it was a very well thought out answer. Whether she was statistically correct or not, I didn't know and had to conclude that she had done the research and was making a choice that aligned with her career interests.
In the end, there is unlikely a wrong answer -- provided it is thought out. Giving the MOC flexibility to place you into different slates is helpful because in competitive situations, it is nice to be able to position a candidate into at least one slate because they were flexible rather than committed to only one option that potentially had stronger candidates.