He is giving advice based upon how someone who designed the cooker, but, has no understanding of smoke views controlling the cooker. You can sweep the ashes with a One-Touch kettle just as easily while using the bottom vent for heat control as the top vent. Just note where the vent is set to, sweep and return within 10 minutes to the proper setting. Smoking is not a process measured in seconds or millimeters.
He is not wrong, but, you will get better results not trapping heat and smoke in the cooking chamber. Let is flow out freely.
I'm feeling bearish, and I'm packing a Wusthof Grand Brisket slicer from MABA
"perhaps...but then again...maybe not..."