It's part of that on-going discussion of how the Abhidhamma expanded the nāma-rūpa
conception from its Vedic milieu, and had to be rescued somewhat by the Commentaries who restored the framework to thinking of the dhātus
as conceptual qualities, rather than just as "things".
It goes to where the focus of the "noting" lies - on the object, or on the experience of the object.
Edit - one of the great things about the Burmese tradition(s), particularly the Mahasi Sayadaw, was the readiness to depart from "orthodoxy" in its description of praxis. The Burmese description of mindfulness of breathing as being contemplation of the wind "element" is probably more canonical than the Commentarial description. Breathing is always found in the formulaic sutta descriptions of the wind element, and interestingly, all of the sutta descriptions of the 4 elements are very abstract in terms of the qualities of solidity, liquidity, fieriness, motion and most pointedly, spatiality.