The reason is that the scarves in the online shop look very tight and possibly created by something else. There is nothing that would prevent the seller from doing this legitimately if that is the case, because Wind Knitting Factory may just be the brand.
I’d like to think the scarves in their online shop are fully knitted by the wind, though.
The part that would be missing from a wind-powered solution is the actual shaping of the sock. She spends a lot of time as she works futzing with the hooks on the machine to create the heel, toe, ribbing, etc. I'm not an expert in what she does, but I see enough to know that if this is just a turbine spinning the machine, you'd get a uniform tube, which would then be post-processed into individual fairly shapeless socks. Hand-crafting would shape the socks better, but the basic tubes are high quality even if unshaped.
There is also definitely a niche-within-a-niche of people who work on these machines coming up with all kinds of non-sock applications for well-knit tubes of fiber. Scarves are an obvious one, but re-working different sizes of tubes to create stuffed animals is one of the more fun ones.