Some breeds of hogs, the Hampshire in particular, can carry the "n" gene which causes it to purge it's moisture when thawed.
Although it is rare, it can show up. Hamps are very lean and desirable to the packer, so they are used in many breeding rotations.
Pork is chilled to 29F, which is considered "fresh". Here in Minnesota I always thought <32F was was frozen.
The majority of the pork we cook for catering is, or has been frozen, without any problems, but we have eliminated the Hampshire breed from our herd.
Good Luck! Roger