spacer car for ore unit trains ?

Hello!

Found this photo on railpictures.net
It shows an ore train behind two Baldwin RF-16 sharks.
But why is there a PRR boxcar between the engines and the ore cars?
It's a spacer car, right? Not a regular (money earning) boxcar, which was pick up (or will dropped) on the way.

Bye

OK, i understand the reason for an spacer car.
It avoid that freight cars, which are carrying flammable or slipping (e.g. pipes) loads, runs directly behind the engine.
But why was this necessary with iron ore, too?

Might not have been a spacer.

The train -- especially if it was an empty train -- may have been ordered to pick up a repaired cripple that had been set out en route.