Clearly, from reading the comments here, most people don't see any difference. However, the argument still stands, and perhaps - precisely because of the comments here - it becomes even stronger: there is no point in using WebP.
The article is talking specifically about portfolio pictures for photographers. I that case, it doesn't matter what most people see, it matters what the person hiring you sees. And if you are doing commercial product photography, the person hiring you is probably going to be an art director who has spent many days messing about with pictures to get smooth background on websites and in print.
