Usually, student or trainee status is required to be eligible for deferment of U.S. student loans. You should check with the policy of the individual program to be sure. Anyone with the job title Postdoctoral Fellow or Brittain Fellow at Georgia Tech has employee status (as this provides the employee benefits options).
Postdoctoral Fellows and Brittain Fellows do not have a trainee or student status.
Postdocs can be the PI on individual postdoctoral fellowships (NIH F32 Individual Postdoctoral Fellowships, NSF Postdoctoral Fellowships, fellowships from private agencies, etc.) under the mentorship of a faculty member.
For all other grants, the Office of Sponsored Projects PI/PD Eligibility Policy states that, "At the recommendation of the appropriate school chair/department head, a postdoc employee may be designated as a co-PD/co-PI.”