In the context of STEM students who focus on inputs, outputs, and engines at the expense of considering societal impacts (or simply telling themselves it's the job of poor humanities students to get elected and pass laws to constrain the most egregious negative externalities of technology) it's asking who an efficiency is for. Efficiency cannot exist in a moral vacuum. As Kim Stanley Robinson summarized in The Ministry for the Future (2020):

… there is good efficiency and bad efficiency, good inefficiency and bad inefficiency. … preventative health care saves enormous amounts in medical costs later, and is a good efficiency. Eating your extra children (this is Swift’s character’s “modest proposal”) would be a bad efficiency. Any harm to people for profit is likewise bad, no matter how efficient. Using an over-sized vehicle to get from point A to point B is a bad inefficiency, and there are many more like it; but oxbows in a river, defining a large flood plain, is a good inefficiency