I can imagine four situations where the title applies.
The ballcarrier is out of the end zone and fumbles when he is tackled. This would not be a safety except for the fumble.
The ballcarrier is in the end zone and fumbles when he is tackled. This would be a safety, even if the tackle had not resulted in a fumble.
Situation #1, but multiple players (perhaps on either team) go for the ball and swat it around before it goes out of bounds.
Situation #2, but multiple players (perhaps on either team) go for the ball and swat it around.
If the offense recovers the ball in their own end zone, then the defender tackling or touching down the recovering player should be credited with the safety. If the ball just trickles out the back or side of the end zone, however, does no one on the defense get credit for the safety?
(It appears that blocking a punt out of the end zone results in that player being credited with the safety, so it would be weird for the defender forcing a fumble that does the same kind of roll not to be credited with the safety.)