I think the reason it's used here is because the one-on-one was surprisingly effective even when applied outside a typical work environment, just like the original usage was that math was surprisingly useful in understanding natural phenomena:
Note that in the original usage of the formula, "unreasonable" meant that there's no valid and explanable reason to why math is so effective in the prediction of physical phenomena. It did not simply mean ill-understood, or explanations to come later. The relationship between math and nature was stated to be akin to a mystery. Most titles borrowing the phrasing nowadays simply mean to say that something is considered very effective and the author finds it surprising.
