>>2124750591000+ people at a time, in a tiny room where they'd have to stand shoulder-to-shoulder and belly-to-back?
without any effective means of de-gassing the room?
with a weak, wooden doors that could be destroyed in a stampede?
The Americans actually discontinued that method of execution because it was deemed cruel and unusual - intimates were surviving for up to 20 minutes. Yet the Germans were doing 1000+ people at a time in less than 15 minutes, according to 'eye witnesses', and they were using far lower concentrations and had no distribution system. With the American gas chamber, the gas was produced in another room and fanned throughout the chamber.
There was also an entire protocol for getting the body out of there without anyone else getting poisoned. Traces of the gas would remain, contained in hair and the lungs. Yet there's no eye witnesses reports of people getting poisoned while pulling dead bodies out of the German gas chambers. Also, the people in the American gas chamber were put in diapers. People being executed usually defecate and urinate themselves. Yet there was no eye witness reports of people having to clean up after a room of 1000+ people were executed.
You can see why they won't ever show it, despite releasing at least two holocaust movies every 365 days