I would like to think that dual-heterodyne is considered the 'traditional' circuit topology, given the instrument's history and development. But what makes a theremin a theremin is its space-control system, which is nothing more than a pair of variable capacitors. Logical circuit designs use no heterodyning oscillator circuits, nor, of course, would a PC-driven software program, employing the space-control system as an external control device.
The theremin was born out of early radio technology, before transistors or integrated circuitry had been invented. The heterodyne principle was, at the time, the most efficient way to create audible electronic tones from an economic collection of electronic parts. When it became possible to generate low-frequency tones on a single, low-frequency oscillator, this technology became obsolete.
Using the dual-heterodyne system in a theremin circuit today is probably neither the most efficient, nor the least costly, and it is certainly not the electronic state of the art. But it does demonstrate the original method by which these instruments operated, and serves as a good educational tool for demonstrating early radio technology.