I will disagree with your statement that shrinkage does not occur in the metal casting process.
If we assume the mold is filled out with molten brass, and the brass cools down to its phase change temperature of 920 degrees C., thermal contraction will occur as the solid cools from just under 920 degrees to 25 degrees C. The piece will pull away from the walls of the mold. The "column of molten brass", if it even still remains liquid, will be trying to compress a solid. That solid will not compress significantly.
As I said, the shrinkage during the casting process for brass is 1.7%. Roughly.