This is all true.

What is also true: If the induction blower/draft inducer/fan-thing/widget is not creating enough pressure differential to trigger the switch that exists just to monitor this condition, then the gas valve will not be opened to begin with. Therefore, there will be no fuel.

Without fuel, there can be no combustion. Without combustion, there are no combustion products. This lack of combustion products does not produce any particular danger. :)