I doubt that 6 hours of college course credit would cause an applicant to be considered as a transfer applicant, but you should check with each school to which your son intends to apply.
Some schools require one to apply as a transfer student if the applicant has 12 hours of college credit, but this varies school by school, while some schools require a minimum number of college credit hours to be considered as a transfer student. In short, check with each school.
I do know that applicants will be ineligible for certain scholarships at particular schools if they have even one (1) hour of college credit.