It is in fact incorrect. The incorrect assumption is nested structure implies nested destructor calls. This can be avoided by ensuring each node in the struct

It is in fact incorrect. The incorrect assumption is nested structure implies nested destructor calls. This can be avoided by ensuring each node in the structure does not destroy the next node_ptr (explicitly or more likely implicitly). Instead, the destruction has to happen more manually (internally to the overall data structure - not by the user). If the structure only recurses on one child, it can be performed as a loop.