While access to economies of scale does create efficiencies, it is not a competitive advantage per se.
If economies of scale are accessible at 10% of market share, that creates room for ten firms with the same economies of scale, which reduces your ability to use economies of scale as a competitive advantage.
In practice, this means that access to economies of scale in that particular market is not a defensible type of efficiency (or, at the very least, it’s not fully defensible).
The same logic applies to anything available to everyone, which is an advantage to no one. Access to AI models is the current example: every competitor has the same models, so they raise the baseline without creating an edge.