Sorry: One glitch in screenshot #1. It should read:
"If a label is assigned, the object does not lose the value of the label in the process"
Just tested CC 2015.2 on this. Bug is there…
I am having doubts as to whether or not this is a bug, with a tendency to think that it is not.
I did not try to script it but ...
If one has a shape and cuts it for example with the scissors tool the one will end up with 2 shapes one keeping the original ID and the other getting a new one.
I would imagine that opening the path is in essence the same as cutting it with the scissors and this explains the result.
I would think this is correct behavior and not a bug.
I thought of this as well.
But in this very special case, it is the order of removing path points to create a new ID on the very same object.
And never in that process do exist two objects where one of it is removed. It's a rare case. I could not repeat it by using a irregular polygon with curve points from the start. Not in the UI, and not by scripting…
Just the steps I'm showing in my screenshot.
Starting with an oval.