You’re right! I wonder how they decided which ones to take pictures of.
They do mention what I think of as “sweet onions” in the story; the second link
For example
“The fact that onions take their sulfur from the soil explains why certain regions produce sweeter, or milder, onions than others. Vidalias, Texas 1015s, and Mauis do not refer to specific cultivars; they’re all white or red grano or granex types, sweet onion varieties that are grown in, and often named for, regions where the sulfur content of the soil is low. Sweet onions are usually sold fresh for short-term storage; the spicier ones, which tend to contain less juice and therefore have a longer shelf life, are cured and stored.”
And
" The kind of onions we’re talking about here are bulb onions belonging to Allium cepa , a species that’s been cultivated since ancient times and now is grown around the world. Allium cepa includes scallions, also called green onions; they’re essentially onions that have not yet developed their bulbs. The same species also includes pearl, boiling, and baby onions, which, interestingly, aren’t just smaller varieties (though some have been selected not to get too big) or ones harvested before they’ve matured. They’re Allium cepa sowed in densely planted patches, so that they don’t have room to grow any bigger than large gum balls. Shallots, which can resemble garlic but contain just a couple cloves, are a variety of Allium cepa called ascalonicum ; there’s a larger, sharp flavored variety popular in French cooking and a smaller, sweeter one that’s the allium of choice in southeast Asia…"
