Hi Mario, welcome to Meta.Discourse.
Both of your links above point to the same topic. But I did find the link to the now closed topic. The second (closed) topic was merged with the first (target) topic and the posts are in chronological order. The flow seems fine.
There is no back link because the topic the posts were moved from is scheduled for deletion in a few days. It would make no sense to have a back link to a topic that will no longer exist. That would be weird. 
However, when posts are moved from one topic to another and where the topic from which the posts are moved from will still exist, the target topic will show a link back to the original topic they were moved from.
Hope this helps explain the difference.