Indeed, it appears that there is no minimum hourly requirements for an add-on Sport rating.

http://www.faa.gov/licenses_certific...ency_check.pdf

So I think the question would revolve around who is the PIC during the add-on Proficiency Check. If the PIC is the applicant, it would appear that he Beard interpretation holds, and he needs a Flight Review before taking the Proficiency Check.