The agent is correct, sort of. You will have access to the Premium Terminal which has a First Class side and a Business Side. They will allow you access based on the boarding card for your onward flight. It is likely that your DOH-HKG card will read business so you will be restricted to that side of the PT.

You can dig into the threads here for the differences, but both sides are fine places to wait for your connection.

FWIW
DLM