I think the person you are responding to used the wrong word when they wrote “irrelevant”, although I think their comment comes from the right place. Even a difference of just a single person is “relevant”. But when we try to comprehend the horror of the holocaust, learn from it and assign blame and guilt appropriately, then the precise numbers no longer matter. It is enough that an unspeakably enormous evil was carried out - the systematic murder of vast numbers of people with the aim of destroying everything about them. Their lives, memories, businesses, art, legacy, children, everything. And in many ways this horrific project succeeded.

With that said, the figure of six million is about as accurate a number that is available. There are good reasons for the uncertainty:

> The two most reliable sources for Holocaust data are the U.S. Holocaust Memorial Museum and Yad Vashem. Though this is the best information available, it is based on estimates and cannot take into the unknown number of victims whose bodies were never recovered or for whom there were no records. The Nazis kept detailed records of the people who passed through the camps; nevertheless, we do not know how many Jews may still have been unaccounted for in the many places where they were murdered. In addition, as the Allies began to close in on Germany, the Nazis began to destroy their records. We also don’t know the precise number of Jews in any of these areas. The population data ranges from 1937-1941 so, for example, the countries where the figures came from 1937 may not accurately reflect the number of Jews at the time the war began. Though the two institutions have different estimates, if you average the total number of Jews each says were murdered, the result is the commonly used figure of six million.

From: https://www.jewishvirtuallibrary.org/estimated-number-of-jew...

It’s not “fishy” at all. History is not an exact science, and the perpetrators of this genocide were highly motivated to conceal their crimes.