I have never heard this claim, in any book I have read regarding Hitler, Nazism, or the Third Reich. It is hard to prove definitively that this isn't true, but I based on my searches, I'm going to call this "highly unlikely" although I welcome an authoritative source to the contrary. The fact that this is a TedX talk - which are of widely varied quality - and not a proper Ted Talk, of course also add to skepticism, but it not proof of course.

In any case, it is hard to write that something *didn't happen, so instead I'd share my methodology here. The following books were searched in digital form for "scent and "smell" in either ebook or OCR'd PDF form to confirm no mention of this was present:

The Coming of the Third Reich and The Third Reich in Power by Richard J. Evans

The Complete Hitler: A Digital Desktop Reference to His Speeches and Proclamations 1932-1945

Doctor Goebbels: His Life and Death by Heinrich Fraenkel & Roger Manvell

Hitler 1889-1936: Hubris and Hitler 1936-1945: Nemesis by Ian Kershaw

Hitler's Charisma: Leading Millions into the Abyss by Laurence Rees

Hitler's Followers: Studies in the Sociology of the Nazi Movement by Detlef Muhlberger

Nazi Propaganda: The Power and the Limitations by David Welch

Nazim and German Society, 1933-1945 by David F. Crew

The Third Reich: Politics and Propaganda by David Welch

The Rise and Fall of the Third Reich: A History of Nazi Germany by William L. Shirer

Aroma: The Cultural History of Smell by Constance Classe

Additionally, a combination of "Hitler", "Speech", "Scent", "Smell", "Emotional Manipulation" and other likely keywords were searched in Google Scholar, my Mendeley library (which searches all papers I have, far too many to list), as well as my institution's journal search portal. Similarly nothing resulted.