Not surprised at all. Those “models” you see in advertisements are often more than 50% fake these days, made skinnier and more “perfect” through the magical wonders of Photoshop.
Addendum: I just checked the H&M site and verified this. A lot of the pictures of models in the sleepwear section have literally the same body, just different skin tones and different faces.
Addendum_2: Wow. They do it for men too. Different men’s clothing are modeled by the same fake “model” body, but with different skin tone and different faces. Whoever works at H&M’s marketing division must be really sloppy and really lazy or something. Either way, it still highlights how Photoshoping and fake bodies are just a part of the business.