They do.
however it is important to remember that GWX 3.0 is a realism mod. In real life, most ships did not break up, in fact they sank whole from flooding more often than not. The Ships in GWX will break up, but this is a very rare occurrence.
Stock SH3 damage models were fare too "arcade like" and almost every ship i ever hit broke in half
I would say that in GWX 3.0 i have witnessed perhaps a dozen ships break in half since the release date.
