Loss of lift due to the interruption of the airflow causing the helicopter to crash into the ground at speed? Or suddenly lower pressure above the helicopter c

Loss of lift due to the interruption of the airflow causing the helicopter to crash into the ground at speed? Or suddenly lower pressure above the helicopter causing it to be "sucked up" into the ceiling. I think the pilot is probably correct that the stunt could only be pulled off at a higher speed where you can outrace the low/high pressure zones the blades are creating.