That oversimplifies the reality. The facts argue for manufacturing excellence and. closely related, highly developed factory operating systems. That is not exactly 'economy of scale'. In fact it is that very flexible production technology that allows Tesla to produce many variants of vehicles while reducing unit cost.
Proof of that is most obviously seen with the multiple battery systems and assembly techniques presently produced all as 'Model Y'. 4680, 2170, prismatic, structural packs, non-structural packs, one giga casting, two gigacasting, AWD, RWD and so on. Those are different vehicles.
In short it is not simple scale. It is manufacturing excellence in highly differentiated products.
Certainly from a naive view, like Moody's, Tesla has four models, only four models, the 2012 Model S and a 2022 Model S are identical aging models. Still, with modest volumes the new Model S is not only superior in all respects but also is much cheaper to build. Modest volume, very high margins. Partly that is because all the variants Tesla makes have the same vehicle operating system. That does give them major scale economies, as does using the same motors (even for SpaceX F9) and many parts in all or most products.
Obviously Tesla has some scale economies that are 'Big Deals' but those are the product of the manufacturing systems, not an independent factor. Typical industrial scale economies are found by using suppliers which sell almost identical parts for many OEMs.
Tesla achieves those scale economies by deploying the same operating system and viewing manufacturing as a product, not simply as a means to an end. Doing that makes them more highly integrated than has been any auto manufacturer since the Ford River Rouge Model T. Ford, though, dealt with pure scale economy. Tesla, by contrast, does it by having the capacity to make dozens of change order a day.
True continuous improvement generates significant differences from day to day. That flexibility is vastly different and more complex than conventional scale economy.