Now, I'm not a structural engineer. However, if at the bottom of the pool you can crush/shear/buckle/etc concrete, you should also be able to crush/shear/buckle/etc six-year-old-girl, right? I'm betting the bending and tension load resistance of 6 year old girls are decidedly suboptimal for residential construction.

I see photographic evidence of six year old girl, decidedly uncrushed.