They started using the word “about” because for many years, they said Jesus established the Kingdom in heaven, THEN war broke out and Satan and his supporters were kicked out, down to the earth where they caused international divisions which lead to WW1.
But some in recent years questioned the timing since WW1 started in July, but the Kingdom was not established until October (according to their timeline. So they inserted “about” so thet they could say that war broke out in heaven “about” 1914 and could have even been before the Kingdom was established. This allowed for the change without addressing the dogmatic statements made about the Kingsom coming before the ousting. Problem solved!!
Words matter with Watchtower and they like to redact dogmatic statements with words that allow them to be right whether they are or are not.