From another thread by the OP:
http://talk.collegeconfidential.com/financial-aid-scholarships/1861066-4-2-program.html#latest
Your child has an undergrad degree so he is considered independent. You might be required to provide info (many post-bacc programs do require this) but that doesn’t affect his FAFSA EFC.
The EFCs are different because one is dependent and one is independent. Simple as that.