It's not the same number. NROTC MIDN don't take the same classes.
USNA uses CQPR, not academic GPA. This includes aptitude for commissioning grades (i.e. MIDN ranking within company), PE courses (Boxing, Wrestling, Martial Arts 1&2, Swimming 1&2, two semesters of PE elective), and PRT (NROTC uses fleet standards, good medium/good high is around the failure mark for USNA) that factor directly into the calculation, in addition to the LEAD academic classes (Leadership 1 and 2, Ethics, Nav 1&2, JO Practicum, etc) and core (Calc, Physics, Thermo, Weapons, Systems lab, EE, Boats/Planes/Dirt, Cyber 1 & 2, Civics/government, Naval History and History elective (European, Asian, or World)). And then we start talking about the major matrix and required electives; for a Group 1 and some Group 2 majors,, standard course load is 18-21 credits.
PRT isn't pass/fail, it's a D- letter grade worth 5-10% (fudging the numbers, it's been too long) of your CQPR if you run a 10:30 1.5 mile. Aptitude/leadership (not the classes, this is your company ranking and company officer/SEL evaluation starting with Plebe Summer onward for each semester, mirrors the fleet FITREP system in that only a limited number of MIDN can get As or Bs) is another 5-10%.
Probably goes down to statistics across the nation for all NROTC units, 2.5 at nationwide average for NROTC is equal to 2.0 at USNA. Some universities suffer from grade deflation. Some suffer from grade inflation. Someone crunched the numbers and considered that USNA counts a bunch of stuff in CQPR that a normal university doesn't consider in GPA.