I think the author is focusing on the wrong thing. They focused on the difference in format, when they should have focused on the compression. Different image

I think the author is focusing on the wrong thing. They focused on the difference in format, when they should have focused on the compression. Different image processing programs will have different compression even when set to the same number (eg "80"). I think for a truly meaningful comparison you'd need to test a variety of images including full color with busy backgrounds as well as these b&w studio portraits on a smooth gradient type bg, and test a variety of programs like imagemagik, graphicsMagick, sharp, photoshop, whatever cloud offerings, etc. The other issue I see is use case. If you're a professional photographer trying to upload full size full quality photos, maybe just don't compress at all so you know your creative / editing work is completely preserved. That use case is not the average use case of a website displaying a reasonably sized image of reasonable quality. For many situations a significantly smaller image might be worth having a more compressed image, and for many images the compression won't be as noticeable as it is in a full resolution professional studio photo with a large gradient type background.