Smartphones - I didn't go to university when I left sixth form, despite having fairly decent A level grades - I decided I wanted to train as a nurse instead (this was back in the days when it was hospital-based, registered general nurse training, on the job, not a degree course).
I qualified as a nurse, and worked for three years, including doing a post basic course in Theatre nursing, and then I decided I wanted to go to university - so I did - and I am absolutely sure it was the right thing for me, at that time - but wouldn't have been right if I had gone straight from school.
Kudos to your son for having done so well in his retakes, and for having got himself this job - and maybe you could see it as a win-win situation. If he does well at the job, and gets promoted, he could have a very bright future with the company or in retail management with other companies - it is a great sector to work in because people will always need to buy food, and shopping is a major leisure activity.
And if he decides, in a while, that this is not the career for him, he can still go to university, but will have experience of work under his belt, which will stand him in good stead both for finding a job while he is at uni, and for making him more mature - he will be in the swing of getting up on time, getting himself to work, completing his work within the allotted time etc - all good skills for university.
I am sure that I was a better student because of the time I had spent nursing - it gave me a good work ethic, and I think I had grown up during those years.
Of course, I am not saying that it is wrong for students to go straight from school to university - it is absolutely the best thing for many of them - but I am sure that some need a bit more time, and need to be a bit older and more experienced when they go - horses for courses.