when you create a basic shape using the shape tools, illustrator treats it as a 'live' shape -- i.e. it keeps track of things like number of sides of a polygon, rotation angle, dimensions of the shape itself rather than its bounding box, etc. Full details here:
Draw, edit, and re-edit shapes easily |
this is evident in the Transform palette, where you can see extra options when you have a live shape selected:

when you move an anchor point, illustrator loses this 'live' shape information and treats it like any other object. that's what the message is telling you.