"Termination from employment" is a punishment and it can be awarded only by the top management. Even before taking this drastic decision, it has to be preceded by domestic enquiry and the misconduct of the employee must be established irrefutably.
Now here in your case you say that if some issue happens with HOD, then HOD may terminate an employee and then HR wanted to conduct the "Termination interview". Both the things are grossly incomprehensible!
How can HOD sack junior employee? Has your company deliberated on the repercussions of this unlimited power? It will make HODs law unto themselves and the worst thing is that it will promote sychphancy as well.
Yes, whenever employee gets separated from the organisation, there has to be "Exit Interview". But then objective of the exit interview is to gain insight. Resigning employee may reveal something that is unknown to the authorities concerned. However, when employee is terminated, the separation has a negative connotation and HR may or may not get a true picture of what's happening in the department.
In view of this, I recommend you revisiting the whole idea of "Termination Interview".
18th September 2019 From India, Bangalore