With all due respect, your understanding is 100% incorrect. Fully inform yourself by going to the USNA website and reading every page, link, tab and pulldown. This topic is very straightforward though sometimes misunderstood.
Bottom line is this: At USNA, your major has virtually no bearing on your eventual warfare community. The only way it really comes into play is with your grades and where that places you in the OOM come service-assignment time.
Some will say this major is easier or that major is harder, hence taking one or the other will lead to higher or lower grades. Don’t get sucked into that faulty thinking. Best way to ensure that you get great grades is to study something you genuinely enjoy. Nothing worse than having to slog through a major you don’t enjoy — amid all the other responsibilities and pressures — just because you think you’ll get better grades. That’s just sheer misery.