>while cotton underpants will vary in fiber content So can old shirts, those are bigger and harder to bury straight up and down, and have no identifying marks

>while cotton underpants will vary in fiber content So can old shirts, those are bigger and harder to bury straight up and down, and have no identifying marks (underwear does have the rubber, which acts as a skeleton and frame of reference for what you're actually looking at; cotton squares don't). Sure, the data might be slightly noisier, but right now they have no data. And that's even worse.