Not quite,
Chandigarh waali also gets mainly filled from Nizamuddin only that too for Pune.
Have traveled in Chandigarh KSK for years during B.Com days used to go to Mysuru to meet parents there.
Decent patronage from Chandigarh Ambala to Pune, it won't seriously affect Nizamuddin, they have other options for Pune.
Merging...
more... of these two will actually be beneficial for all. Nizamuddin yard would get freed up without compromising much on seats and Chandigarh would get more days of connectivity.