Avian X half inflated?

I just picked up some Avian X topflight Mallards that were on sale and noticed that the backs of the decoys can be pushed in about a 1/4 of an inch relatively easy. Is that by design or did I get a defective set?

By design. Even shot up as long as no water gets in they still float....they are not air dependent.

By design. I also think them being softer helps to keep the paint from rubbing off as easy.