The original comment was unclear whether the fan kept spinning while the furnace was running, or if all it did was bypass the safety and the fan didn't continue to spin while the furnace ran. They clarified in their response it 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.