But economies of scale are independent of the supplying market - having one skilled industrial engineer (who may be the owner) set up a fully automated line to make screws would be an economy of scale as the automated would sustain a lower price per item vs a manned line or masses of tinkers machining every screw by hand.

Said situation also says nothing about your suppliers as a bunch of small steel producers vs one massive steel monopoly themselves.

The economic power wielded is a maximia of the difference per item in efficency essentially - as any attempt to leverage it would result in the old less efficient way being cheaper and negate the competive edge.

To call the hypothetical sole industrial engineer "dictatorial" is quite the strange definition.

Automation and production efficiency isn't what people mean by "economies of scale", though, especially in relation to antitrust. When large companies make gains from "economies of scale" it's almost always because they've attacked margins, usually by wielding enough power they can convince suppliers to make less money, sometimes by replacing other parts of the vertical market by doing things in house.

If you think about the tech giants, they're not making gains by automating more production. They're buying up fiber, building their own chips, creating their own shipping companies, etc. They are big enough to alter most markets in ways that are favorable to them.