Is This A Bug?

I have a dupliverted set of spheres that I made real. Then I duplicated the resulting meshes and parted them in edit mode. Next I made their material a single user. I hhave Blender set to the default setting so that it will NOT duplicate ipo’s with the mesh, yet the material ipo was duplicated anyway. When I delete the ipo from one mesh the ipo of the other is deleted also even though these materials are single users. I could easily recreate what I want but I’m trying to find out why this isn’t working as planned. Is this a bug and has anyone else had similar problems? Research hasn’t yielded any results, but I don’t want to waste the dev’s time in the bug tracker if this is a known issue. Those guys are really busy.