I really don't mind you using my examples of activity posts. Especially because by doing this, you again brought up the fact that there's still something faulty in the (older) activity posts. As you said, the Activity Timeline Bar should reflect all posts we have ever created, preferably only in the GEC. (My activity timeline also shows some posts from other forums).
I guess the reason why my activity bar shows more entries is just that I frequently edit my older posts if I spot errors, or want to add an additional link.
What actually does work, is the ability to edit all our (older) posts we have ever created, so the migration has fully worked and our user names are now connected to our older posts. But somehow, I feel they are just not 'activated' yet. To test that, I have opened a post from Jan 17, 2009 called "Sheep Cruisade", edited it and saved it again. And guess what, it now shows up in my Activity Timeline Bar..
So the problem still need to be looked upon. Our user names are now linked to all our older posts, but there should be some automatic way that the engineers need to come up with, to somehow mark / flag / activate them as being 'edited'. When this is done, all our posts would probably show up in our timeline.