It only behaves differently because some c_set/c_hull bugs have been fixed and the bounding box is now set at entity creation and not in the first frame (AFAIK).
Remember, you can always use d3d_lines or press F11 twice to show the bounding box of impassable objects.
"Falls das Resultat nicht einfach nur dermassen gut aussieht, sollten Sie nochmal von vorn anfangen..." - Manual