Missed opportunity by not making the blue and yellow ones a Great Ball and Ultra Ball.

A simple explanation of the picture (and that's all it is, don't make it more than that. Please, God)
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This isn't bad anatomy, her body anatomically correct.
It's a bad perspective that leads to the error.

He went for a pose, right leg in front of the left (if any were wondering about that, too) of her standing slightly to the side while twisting her upper torso towards the viewer. Of which, if you look at her shirt, he pulled it off.

The bad perspective comes in with the opening of the shirt, where he, clearly, wanted to maintain her appeal, but focused too much on her cleavage (obviously, to do that, she'd had to be positioned more to the side, with our angle being a bit above her). That error leads to the error that is simply the placement of the crevice between her breasts.

And, lastly, the neck isn't thin. It's long, but not to point where it's completely off putting.