Designing something people want to buy at scale is high skilled work, sure
If it didn't require above average skill or more, it would mean your average Joe on the street should be able to come up with patterns that will sell above average. (The latter of which might be plausible at the end of the day. But professional cloth designers will probably beg to differ and/or raise that it's a recipe for lack of creativity.)
There's a wide spectrum between average and high skills; the parent referred specifically to high.
Besides, the article, which is very poor and click-baity, starts with a factoid (algorithms designing shirts) and then steers into something completely different - big data.
You try designing a something on a shirt, sell it on Amazon, and see how many people buy it.