The typical camera lens is optimized to image objects at different distances and project images onto flat film or image sensor. A macro lens, on the other hand, is optimized to work flat subjects. Also, be aware that most macro subjects are flat like postage stamps or objects with limited thickness (contour). By inverting a “standard” lens, the rear elements, optimized work a flat, yield improved resolution when tasked to work in close.
Additionally, the object distance measurement is subject to forward nodal point. Whereas the focal length is a measurement taken rear nodal to image plane. These two cardinal points likely do not fall at the center of the lens barrel. In fact, they are likely spaced apart and they can even be flipped placing the rear nodal closer to the subject. Thus, inverting the lens improves resolution and likely grants a little additional magnification.
These improvements are likely to subtle meaning, don’t expect magic. In other words a true macro is your best bet.