I've had this conversation with DS over the last three months (he's a junior shooting for USNA with engineering interest but his primary goal is to be an officer). I did ask questions on this forum about USNA rigor w/r to engineering and did some due diligence with colleagues, SA grads that are now engineers, and engineering professors at engineering-heavy schools. I am satisfied that USNA does a very good job of laying the foundations for engineering for the disciplines they offer majors in.
I think it is important for anyone going to SAs (and non-SAs) who eventually wants a technically based engineering career (as opposed to a management/leadership career) to understand that you really need to think about going to graduate school - an MS for sure. That's not to say that you cannot have a technically based engineering career with a BS (many do) but it is now becoming much more common to see MS degrees with additional specialization. The advantage of entering an MS program is that you have the opportunity for (a) "remedials" - i.e. undergraduate-level classes that fill in the specializations that you might have missed in your undergraduate program or background classes you may need if you are, for example, pursuing a civil engineering MS with a mechanical engineering BS and (b) developing specializations through graduate research, graduate-level classes, seminars, etc. that make you more prepared. Engineering programs at the undergraduate level, first and foremost, train young minds to become problem solvers. That's what you do in undergraduate engineering programs - you become inculcated in solving problems. Many undergrads in engineering never realize what's happening to them - then, one day, when they're at home trying to figure out why the garage door opens when they turn on the bathroom light, they use those problem solving skills for something totally unrelated to what they studied in school. I suspect (very strongly) why the SAs are so focused on engineering - it is great training in becoming problem solvers of the first degree. To solve problems, while under stress seems to be what they want and need in an officer.
I'm confident that if an SA grad with an engineering degree five-and-dives (or even longer service), they will be well-prepared to enter a grad program and with a bit of "remedials", have a great technical engineering career - because they have been prepared with the basics, know how to solve problems, and have a all the other things that their civilian classmates may not have (leadership, maturity, confidence, experience, work ethic). I've seen this first hand. Thermo, statics, diff-eq, dynamics, SofM, fluid mechanics - they are the basics of engineering and they don't change with time.