It may have to do with the CORE having a different trigger/sear assembly that does not accommodate the magazine safety.
Not sure if this is true, but I have both a FS and CORE, and they are different. In fact, the opening in the poly frame where the assembly drops in is different.
Since CA has the 10 rnd limit, and requires a "no mag" trigger disconnect, S&W maybe didn't want to bother handicapping this competition model.
In USPSA, STEEL and IDPA matches, you are required to remove mag, show an empty chamber, and pull the trigger before holstering. This is a safety requirement after a run. Can't be done with the CA versions.