Those guessing about taxes are wrong. When you add up all the taxes taken out for the bonuses or lump sums, the OVERALL tax rate is around 40% as it always is. The Federal tax rate is 25% (see link below, section 7), CA is from 5-10%, social security and medicare is 7.65%, and then there is CASDI. Companies don't have a choice in how much they tax. And they don't hold onto the money--laws require quick payment to the state.
There is no choice when it comes to taxation. No "lesser amount" they could have taken out.
https://www.irs.gov/publications/p15/ar02.html