If they don't contain him now, when Song Chongjin truly becomes a Scholar and captures the attention of the current times, it's possible they won't be able to control him anymore. After all, the civil and military are distinct, and those scholars, as different as they may be, when it comes to dealing with military generals, they act in unison.
If it were possible, he wouldn't want to do it this way either, as it hurts the father-son relationship too much.
But is there any other choice? Outsiders see the Duke Weiguo Residence as flourishing, deeply trusted by the Emperor, a pillar of the state.
The family members, one by one, only know how to enjoy the present conveniences of the Duke's Mansion, not seeing the crisis behind this splendor.