Probably just confused by the questions in the 1911 census, which asks for number of children born to this marriage and how many are still alive.
When listing their children, the deceased were included with their projected age, but there was no provision for date of death.
They did their best to provide the required information, which wasn't quite right, and was crossed out somewhere along the line. It's impossible to say if this was before or after it was handed in, but these mistakes can be an unexpected boon to researching the family.
Colin