They were told they were being given showers, and there were fake showerheads installed to continue the ruse. There were no pipes connected to the showers, the Nazis dropped canisters down chutes. The shower contrivance makes sense as a way to get them to strip “willingly” to get at any last valuables hidden in their clothes without having to bother with the bodies.

I think the popular imagination goes to that scene in Schindlers List - the very tense scene where the Schindlerjuden get shipped to Auschwitz and we don’t know if they’re going to be killed or not.

This is something we have to be careful when talking about - because all of those complicated discrepancies between memory and rumor are the muck Holocaust deniers like to throw everywhere. I found an online “uncensored Holocaust encyclopedia” on the first page of DuckDuckGo before I found this link.