Lots about the stones; not much about why 'Homo Sapiens'. Is it just because these tools are attributed to Homo Sapiens? I skimmed the article but didn't see anything about human remains or dna analysis.
The whole paper is about microliths, which are only known to be associated with anatomically modern humans (AMH, aka us). This is just "general background knowledge" in the field, so they don't spend any time explaining or analyzing it in the paper.
The particular typology they use here (shea's modes) is also more complicated on this point than the traditional clark framework where you can just say "mode 5 == AMH".
There's a ton of archaeological research into human-made stone tools, worldwide. There's very high degree of confidence at this point into which artifacts can only really be human-made, versus made by other animals or natural processes. My guess is organic evidence of human activity would be really unlikely to survive in the South Asian rainforests, so I'm guessing this one of our better sources of information on human activity there.
If you're asking how do we know this refers to Homo Sapiens, versus other species in the genus Homo, I'm guessing we can't really tell that.
