Ask HN: Why does the CA Pay Transparency Law only address base pay?

The new CA regulation regarding pay transparency only addresses base salary, but not stocks or bonuses. Employers can continue to do whatever they want with stocks without being transparent about it. There can be great disparity in stock grants for existing employees in the same role, or for new hires even if they get the same base salary. Same concept applies for bonuses. What am I missing in interpreting the law or its purpose?