Sure, and dust, and any other spores or pollutants in the air, I didn't mean to provide a pure and complete list, I just meant that it's not some magic yeastless concoction that also happens to make bread rise. It's still yeast doing the work, it's just naturally occurring, rather than added from a packet of commercially grown and sold yeast.

Right, but that article claims that lactobacilli are critical to make the bread actually taste like sourdough at the end, whereas presumably dust isn't.

I did realise your main point is that it does include yeast, and I agree with that.

Oh yeah, absolutely, I just meant that all (leavened) breads contain yeast, I suppose it's a defining feature; so it's not 'yeast vs. starter', it's 'yeast from a packet vs. yeast from the air'.