I was reading the article on J002E3, and it mentions that most other S-IVB have entered the atmosphere and mostly burned until reduced to relatively small pieces. They did, however, enter the atmosphere with less energy than J002E3 would have coming from a Solar orbit and (I assume) entered on more or less tangential trajectories.
The question is, would such a stage of a rocket burn more or less, if it were to enter head-on into the atmosphere?