FWIW, Macromedia Freehand exhibits some of the same kinds of problems in duplicating paths for a variety of operations. I haven't seen the Illustrator style duplicate layer thing, but you will still get duplicates on some tasks.
For example, I like to use Freehand for creating outline paths around letters or other outlining effects. IMHO, Freehand is more accurate at doing this than CorelDRAW or Illustrator. You end up with paths that are more accurately drawn and with far fewer control points. Corel's contour effect generally creates paths with many hundreds of control points (mainly anchor points joining straight line segments). And then Corel's convert outline to object command often creates paths with all sorts of wierd control point problems. Illustrator is a good bit better, but still often deals out some contours with lots of path trash. For what I do, it is very important to have very clean paths. I don't want a CNC router glitching out because it reached a stretch of G-code that was all gummed up due to some screwy path routes or 7 control points aligned to the same spot.
Anyway, to get back to the point about Freehand's issue with duplicate paths, often when I use Freehand's expand outline function and remove overlaps xtra I'll often get a duplicate of the original source object. This mainly occurs with compound paths.
I'm waiting on delivery of IllustratorCS2. I'm hoping its capability for outlining objects and such is improved over some of its past versions (mainly 7 through 10).