I work on the non-Perkins side of the student loan world, so this might not be exactly the same for Perkins- but I'd guess it's close since credit reporting guidelines and rationale for them apply to all types of credit.
If the Perkins loan was "subrogated" or assigned to ED, the first holder (university) would probably need to delete the tradeline, and ED would report from there.
However, there is a code non-guaranteed loan holders can use to show assigned to internal or external collection (status code 97). If the Perkins holder can use that code, it would still show as a tradeline, but I'd say the balance should zero out since credit reports don't want double balances showing.