Factual error: The word "intel", used several times, is first recorded in 1961. It certainly wasn't in use in 1918.
Factual error: When Steve gets dressed after bathing in the pool he zips up his fly. The film is set during the First World War. The zip was not used on clothing until 1925 and did not become common on flies until long after that.
Factual error: When people are celebrating in Trafalgar Square in London after the end of WWI, someone can be seen holding a portrait of King George V. That portrait was taken in 1923, five years after the end of WWI. (02:07:39)





Answer: It would be more accurate to say they grow to a certain age then stop aging. Similar to the elves in Tolkien's Lord of the Rings.
jimba