That was not our experience.
During recruiting, the coach told my D22 she would be “eligible” for the school’s largest merit scholarship based on her academics (outside of a few special full-ride scholarships that required a separate application). The coach acted pretty confident about it without making any promises.
Indeed, my daughter did receive the highest level of scholarship with her acceptance, but I would have expected it even if she was not recruited because of her GPA, class rigor, test scores, etc.
Are the schools that have awarded your son merit aid as selective in terms of admission rate as the school where he was recruited? If so, it would be bizarre to me if they decided to withhold merit awards from athletes that they would award if the athletes were not recruited. If that were the case, they soon wouldn’t be able to field teams except with walk-ons!