Hello Artur,
I see your point, and it resonates with things I have thought. In the period in which I am most interested, the exact original etymon of MIA sutta is largely irrelevant—what is crucial is knowing how the term was understood in the period, namely as equivalent to Sanskrit sūtra—and therefore I have not intervened in the discussion. I believe in the philological method, and in the absolute need for its technical rigor and intricacy. At the same time, I personally envision philology as a tool, a wonderful tool but a tool after all, that can allow us to enrich and deepen our knowledge of a social, historical, or linguistic past. I understand, though, that other people do treat philology as a goal in itself, and I have no objection to that.
However, I am not sure whether this is exactly the case here. In the specific case of the etymology of MIA sutta, I would argue that knowing what exactly the practitioners of the śramaṇic religions viewed as closest to their sacred discourses can indeed tell us about ancient social understandings, affinities, or tensions (did they envision their texts as more akin to the Vedic hymns or to the orthodox ritual manuals?) and about the chronology of those dynamics.
I wish, though, that when engaging not only with the general public but with the field itself, we could be more explicit about the social, historical, or linguistic relevance of a given philological problem. What exactly is at stake behind a technical conundrum is not always crystal-clear even to the professional.
namaskaromi,
Diego