Many fruit beers are made by racking to secondary on top of the fruit. If the "secondary or not" debate has a neutral point, this is as close as it gets. If you do some research on fruit beers, racking to secondary is the normal procedure.
The reasoning is that the vigorous phase of primary fermentation removes much of that fruit flavor that otherwise would be available if added in secondary. Maybe the recipe already has that taken into account since it says to add it to primary.