"life casting is more suitable to depict static postures" is a fair argument against using it for this piece.
But just saying life casting "ain't art" is, again, a very narrow view.
And frankly, the issue with this piece seems to be the fact that it's a bad pose, life cast or not. So to me, it being a life cast (or not) is a moot point.
If the piece *worked* and it was a life cast, I couldn't give a rat's behind how it was made.
And that's for all the reasons I described earlier... I don't think a photo is less art than a painting just because it used a mechanical technique to capture reality.
If you want to say life casting takes less skill than modeling from scratch, I won't argue that point. If you say it's less art, I say I'd have to judge that piece by piece.
Would it be ok for me to say that a non-life cast but fairly exact representation of a person (or animal for that matter) isn't art because you are merely copying something that already exists? Would it be ok to say that abstract pieces are better because they are not merely copying the real world?
I wouldn't say those things, I'd have to judge it piece by piece. I'd never want to judge a work of art solely on the technique used to create it. And that's why I don't really care if it's life cast or not, I only care if the final piece works or not.