Lets forget the American definition for "muscle cars". It is a definition for American cars. We are Australian and our cars were built to suit Australia. To me an Australian muscle car was built with touring car racing as the goal, not drag racing as in America. So that would include A9X, L34, E38 and E 49 Chargers, S4 EH, all the GT falcons, XU1 etc etc. Clearly not a panel van or ute no mater what similarities they had to the sedan versions. They had n handling upgrades or performance improvements over the joe blow sedan or station wagon that mum or dad would buy to go shopping.
They were aimed at a target market of youth culture and they did that with great results that I would imagine made Holden good money in the day. All they needed to do was pick the right parts from the already developed parts bin and make them stand out with a sticker kit. No track or race development was used specifically for a Sandman.
They are a lifestyle vehicle and today they would be called a sports utility/van. Thats what they are.