I see, the article has a contradiction: 'Now I don't think Chrome has implemented this feature in any other way from Firefox, except that for some unbeknownst

I see, the article has a contradiction: 'Now I don't think Chrome has implemented this feature in any other way from Firefox, except that for some unbeknownst reason it is a lot slower, but I do think that the two browsers decode images in a different way.' It's a result of conflating the decoding itself, which is identical, with how images are swapped in or out.