That might be true, it probably is true - but Trump was impeached when he was in office.
TY. Sometimes the term ‘impeachment’ is used in the context of the full impeachment process =impeachment vote + trial.
It is however important to be precise with terms at least for education and avoidance of misunderstandings.
The sentence should have been written:
The same applies to ‘any part of the impeachment process’ for non-office holders