His trouble stems from his belief ( Shared by other NRI US citizens) that OCI (Overseas Citizen of India) is Dual Citizenship. It is NOT. OCI/PIO card scheme idea is probably based on Green Card of US. Which gives you almost all the rights of US Citizen except Voting Rights and be elected representative. But there are few differences. Two major ones are:
Like US Green Card, OCI card cant be used as Visa to enter India. OCI/PIO card holder has to send his Passport to Indian Embassy which will either Stamp or apply sticker of Permanent Multi Entry Visa. If Passport is changed or renewed than New passport should be stamped or one has to carry Old passport which has Visa stamp/Sticker. Failure to do so means you do not have Valid Visa to enter India. ( It is more like coming to US after a year with only Green Card without Re Entry permit). Carrying OCI/PIO card will not give you entry.
Second difference is that OCI Card holder is not liable to pay Income Tax on his/her Income not earned in India.
Whenever one has to deal with India ,it is always better to read ALL FAQs. They provide more info than the main page.