Those particular numbers include both scholarship and non-scholarship but I would say the majority is non-scholarship. A lot are lost to poor decisions - drinking and driving, barroom brawls, not meeting academic requirements, figuring out it's just not for them. Some decide to just take a different path like PLC or OCS directly. There are all kinds of reasons. However, if you are determined to become an officer and don't do stupid stuff, it's certainly possible to complete it.
I would say if a Marine Option performs well in the program, does well academically, and meets physical fitness standards, then they can earn a scholarship. It is still a national competition and is driven, in part, by the needs of the Corps, but it's doable.
I would add, if my son can do it then anyone can do it. I always thought my son could do better in high school. He was a solid B student but I knew he had more in him. He worked hard at wrestling, and I could see his leadership potential, but he wasn't exploiting it. NROTC lit a fire under his butt. He developed into a terrific leader, and I can see some of those skills in phone calls I happen to hear on occasion. He made the Dean's list 6 of 8 semesters in college. He got 300 on his PFT at the end of each semester (he liked his picture on the wall of the ROTC building). He is now a Captain filling a Major's slot, responsible for developing and providing new capabilities for the Corps.
Your son can do it too if he has the heart and desire. Good luck to him. Hope he wins a scholarship but all is not lost if he doesn't. As you know he can enroll as a college programmer. There are also other paths to a commission including PLC and OCS if for some reason NROTC MO doesn't pan out. One of DS' roommates dropped from the program for various, well thought out, reasons. Today he is a Naval Aviator.