In witcher everything is pretty much static so physics are probably not as inensive for the most part, you cant jump or reach alot of areas. We have to consider that a player can jump on the roof of a house and whatnot. npcs are pretty static and most of them dont really interact. you cant really bump them or interrupt them. Then there is also the time it takes to populate a large fully explorable world rather than a focused area, so resources are something to consider. You cant loot bodies, they also dissapear immediately. Most doors are locked and cannot be openned ever. I mean there is a ton more Im not covering but I figure I can share a little insight from a devs perspective. That being said I do think Witcher 2 is doing some great things and am really enjoying it when I have a little time.
Jumping and bumping into people confirmed? I hope this doesn't get you in trouble vsions... Cause, ya know........ Olivejuice.