It was common for ships to be built slightly out of sequence according to hull number. Specific warships were assigned their hull numbers long before they were ever built. Contracts were issued to roughly schedule the construction sequence according to hull number, but once the contracts were awarded the realities of wartime production took over. The ships were laid down whenever the allotted way was freed up, regardless of hull number order. Ships were being built as fast as possible, and the yard building the Wisconsin was little bit faster to complete her than the yard building the Missouri.
Regards,
Chris Friedenbach
Crewmember, SS Jeremiah O'Brien