Yeah, that would be my assumption too (based on my admittedly incomplete personal experience where I got my furnace running by manually spinning my draft inducer motor, which kept spinning).

As exhausting the combustion products is a critical safety feature, I would be surprised if any furnace was designed such that it could possibly keep running if the draft inducer motor stopped. It seems like it would be trivially easy to make a circuit such that gas valves could only open if the draft inducer motor + fan wasn't spinning.