Why is the title of my post not updated?

You can adjust every steting of a post individual for each channel you want this post to be published.
In the newsdesk overview, however, the title will remain unchanged. 

If you want to adjust the original title just click on the title in editor mode.

Editor mode
Hover over the post in the news overview and click on the pen icon that appears on the right to open the post in editor mode.