Maybe he meant F line for security, not immigration, many airports in the world has it. But I have to say, HKIA is so freaking efficient, never waited more than 5 minutes on security line (but immigration is another story, those lines are long, so I guess the OP really was wanting an F immigration line, but then again, if he comes to HK that often to worry about it, he should sign up for e-channel, never more than 30 seconds.)