It's not about Major. It's about what AROTC calls "Academic Discipline Mix", or ADM for short:
Nursing: ADM5
Engineering: ADM4
Math/Science (aka Technical): ADM3
Social Sciences/Biz: ADM2
Humanities and Arts: ADM1
Notice that the Scholarship award letter stipulates without using the term ADM what your ADM is-- does it say "Technical" or "Engineering"?
Anyway, to move from a higher number ADM to a lower number ADM requires Brigade approval. Might be easy to get or not easy, varies from year to year. Your Cadre will process the request and see if it gets approved. It is harder to jump to ADM tiers than one. The Army is trying to increase the number of ADM4 and ADM3, so moving from those on down will get some initial resistance, but my bet is that it will be approved.