· Just a guy who plays saxophone.
The posture is important regardless of strap choice and bad posture habits (in general, not just while playing) are what lead to problems as we age. As long as it does the job of holding up the horn I wouldn't worry about it unless he complains. If he's still playing a lot late in high school and continuing beyond is when I'd start thinking about a possible change. For now just don't be the parents that leave a kid with one reed that's chipped and no spares