It's an old engineering jibe, of course :) I suspect that the engineer in the GP's story might not remember the equations for angular acceleration, but has an

It's an old engineering jibe, of course :) I suspect that the engineer in the GP's story might not remember the equations for angular acceleration, but has an intuitive sense that if a spinning something is in contact with a non-spinning something, you need a good reason for why some of the energy won't get transferred from the former to the latter.