Honestly, I don't think that was really meant to be an oversell and more of an actual bounce. This can be debatable, but I can't seem to see how RVD would spring himself back up that high.
My best guess is that he tucked his head and landed on his shoulder line. I've kept my eye's on his hands and he isn't pushing off the canvas at all.
The bounce is only cause of Tommy Dreamer. At the very last moment he brought his legs up a bit so RVD's head would go directly into the canvas and possibly cause Spinal Injuries. If you watch closely you can see Dreamer snapping his knees up just as impact happens so RVD's head wouldn't entirely hit the canvas.
If your still wondering how RVD's bounced so high, even if Dreamer used he's legs from the position it be impossible for Dreamer to get RVD that high. On the contrary. Dreamer is, if not one of the physically strongest ECW Wrestler. He could be doing moves like John Cena but Dreamer enjoys his style, and finds it safer, and his move-set is a bit more old school compared to Cena's.
That and RVD kicked his legs up to add some momentum to the bounce.