Language can be such a wall 
I did the steps your explaining
This is exactly what I wanted to say!
Have you also seen the Linked mention pane?
Even though you changed the header, the pane displays a link to note A stating [[note B#Header-1" as being the link?
I do believe this is not correct behaviour (?) and I also could interpret that this is the behaviour you were mentioning (still faulty in 0.8.8)
That’s the strange behaviour I was looking for in my bug report that I couldn’t reproduce directly. Thanks for helping me there!
When you add the text Backlink to note A under Header-2 (changed) in note B Obsidian correctly puts this phrase in the Unlinked mentions referring you could possibly backlink note A in note B by enclosing note A in [[]]
When you do that the backlink is correctly put in the Linked mention pane under note B.
Again when any changes are made to the header we come in the same ‘faulty’ behaviour explained.
Babylon issue resolved I think 