the area beneath her far breast suggests a very strong curve to the spine, but the place where her backside connects to her lower torso makes her entire upper body and ribcage seem very thick in the forward/backward dimension
and the way we can see her vag/taint area head on also makes the implied shape of her pelvic area way off.
seems to be several levels of subtle fuckery going on in this image
I think the problem with this image (if any) is the lack of shading rather than anatomical nonsense.
When compare her pose to real kickboxing pose, it is kinda extreme but not impossible. The lack of shading on her right side (the connection of the right upper and right lower quadrant) to suggest how contracted her body is when doing this pose is what is off here.
the area beneath her far breast suggests a very strong curve to the spine, but the place where her backside connects to her lower torso makes her entire upper body and ribcage seem very thick in the forward/backward dimension
and the way we can see her vag/taint area head on also makes the implied shape of her pelvic area way off.
seems to be several levels of subtle fuckery going on in this image
Even considering these points fairly as being possible issues, I'm still very much of the opinion that whatever might be wrong here isn't enough to be calling it "nonsense"
If whatever is wrong here can be described as "subtle", then that's hardly on the same level as the "oh my god what is even happening here??" feeling the phrase "anatomical nonsense" invokes.