One thing that's often overlooked in these discussions is that the VTT isnt just about constructing subobjects correctly its about simulating the illusion of identity for each base during phased construction. The virtual VTT entries exist primarily to support downcasting and method dispatch in contexts where the derived object is not yet fully formed but the language semantics require 'as-if' behavior. This is particularly relevant when you have virtual inheritance across multiple independent branches of the hierarchy that must reconcile shared virtual bases. You're essentially encoding partial object perspectives with temporary vptr adjustments, allowing each base to 'believe' its the most derived type during its own construction.