I don’t get the implication that it wasn’t done with government funds or off government time. It certainly sounds like an official trip, though not a standard procedure. Some executives are just more hands on than others.
In the article, Dianne said he went on a personal trip. She didn't say an investigative trip or an authorized trip. She could have left at as "he went Benghzai" but added "personal" to the statement. To me that means he went on his and outside of the government.