Yeah but women with PCOS are fat all over

Nope, think again. In addition to being fat all over women with PCOS also develop higher proportions of belly fat due to fluctuating testosterone levels. This is not unlike beer bellies that men develop.

This, combined with bloating can lead to a distended belly similar to the woman in the picture. I know because I have PCOS and yes, it can get that bad. I had people personally come up to me and shamelessly ask if I was pregnant.

There is no universal 'look' to PCOS. You cannot diagnose or undiagnose someone based on how they look, especially if they suffer from lean PCOS. Look up pictures of 'PCOS belly' and you'll see a wide range of stomach, many to the point of appearing pregnant.