I also read the rumor briefly but I didn't explore it in more depth because it was still not really official. But if that could really happen to Dortmund, I would also be very worried about Dortmund's condition because Ten Hag is not a coach who has many unique tactics so the development that Dortmund itself will get may not be much different from what they are currently experiencing. And at this time I also wonder if there is no one else that Dortmund can look at other than just Ten Hag, because Dortmund really needs a coach who is experienced enough to develop a team when it is in a slump like now.
I agree to your point, Ten Hag isn't a coach that will successfully see a team through development and get them good success, I know some persons may want to argue that at Manchester united, he was able to achieve two trophies and that made him appear like a coach would can be addressed as a good one but if we look at his performance in depth we get to see that there's no tactical fluenc, it's just basically survival pase he's been going with and probably looked like he just got lucky and the Bundesliga has got a very fiercey approach that needs beyond just survival strategies if you must maximise results from the German Bundesliga.