It’s actually possible to die from side effects related to withdrawal from opiates. Pure withdrawal in an otherwise healthy person, no, but someone with say myocarditis (common in IVD users) going through withdrawal will need careful management. As a HCP I know that pure alcohol/benzo withdrawal are the only two withdrawals that commonly kill, but it is still possible to die from opiate withdrawal and it’s important to distinguish that it should be medically managed as well.

ETA: This paper describes other common mechanisms of death during opiate withdrawal, namely vomiting and diarrhea.