Just watched The Captains on Netflix.
Was anyone else doing some mental math when Shatner was telling Patrick Stewart about doing a school play when he was six about the Holocaust? Shatner was born in 1931. Making him six years old in 1937. And ten years old when the US entered WW2 in 1941. Shatner tried to make it sound like he was in grade school after WW2.
Well, Shatner is Canadian, and Canada entered the war along with Britain when Germany invaded Poland in 1939; the U.S. entry date is irrelevant.
And his memory of those events might just be fuzzy and mixed in with other memories. That's a fairly common occurrence, especially as we get older and try to remember events from our earliest years.
Also, Nazi abuses against European Jews commenced long before the explicit extermination program now known as the Holocaust began. The play may well have been about the earlier anti-Semitic laws and actions, which Shatner equated with the Holocaust, either erroneously in his memory, or in his own personal opinion (since it's not like there's a clear-cut definition about what particular act of oppression against European Jews does or does not qualify as being part of this event we call the Holocaust).