No, economists pretend they're presuming such harmless, innocent instrumentalism to hide the lunacy of their model's assumptions. They assume people's economic behaviour is consistent and predictable so it can be quantified. That way, economics can be as exact as physics, in theory.

But when economists have to elaborate on what it means to be "maxumizing your utility," they end up positing thicker notions of calculation, to prevent inconsistency/irrationality from interfering with their simplistic formulations.

In short, economic rationality must be anti-Freudian, with no disconnect between the conscious and unconscious minds, and with perfect self-knowledge and information. The limit case of the economically rational person is a computer since only a computer's calculations would be perfectly consistent.

A person, however, can be confused about what she wants, or she could be pretending to want something to please one audience, while she secretly wants the opposite. There are all kinds of emotions, instincts, and social factors that get in the way of these predictable instrumental calculations the economist posits. That's why the economist's concept of rationality ends up distorting rather than clarifying economic reality.

Very quickly, then, this talk of harmless instrumentalism takes us to the thicker concepts of rationality, to the anti-Freudian abstracting away of emotional inconsistency or mental modullarity. And the economist equivocates on what she means by "rational," depending on her audience. The fullest conception that makes the most sense, given the libertarian foundations of economics, is the sociopathic model that's based on robber baron behaviour.