This came up this weekend; as I rarely face drop pods locally, it was new to me.
A drop pod came in and scattered. My opponent claimed that it slid across the table, but stopped if it couldn't pass between two other pods. It ended up scattering less than half the full distance, and wedged up next to the pods already down. The full scatter would have put a dreadnought where my heavy weapons could have shot it, rather than behind a wall of pods.
My reading to date has suggested that the move backward is only to avoid landing on impassable terrain or troops, and isn't a slide across the table. Since I wasn't worried about it, and had no inclination to hunt up rules at the time, we went with it as he said. I just wonder which way the rules support, for future knowledge.