If the foreskin will not retract behind the glans when flaccid, it is very tight. That is the likely reason they recommend the circumcision.
The alternative would be for him to pull it back every day as much as possible to stretch it, using baby oil to help, and to wash it afterwards with soap and water to remove the smegma. The only risk is that he could have an episode of paraphimosis. With erection, the glans ends trapped behind the tight foreskin, with risk of it dying from inadequate blood flow. It requires an emergency circumcision.
This case shows why parents need to conquer the fear of teaching their sons proper penis hygiene when they bathe them. The child should be taught to pull back the foreskin and wash, and that over time, the glans will detach and appear, the foreskin eventually gliding easily over it, and if not, to gradually stretch it. It should be checked that the child does it every time he bathes, so that he does it routinely by the time he bathes alone.