some (not all) of these people are highly leverage as in they use the future proceeds from the stock / options allocations to purchase homes now and essentially grant these options to the lender as collateral. When the value of these options decline, they get essentially what amounts to a margin call from the lender, and are forced to put up more of their future allotments as collateral. If they become too leveraged or cannot meet the margin call, guess what happens.
In addtion to this, since they do pay tax on these option grants (almost immediately upon the grant) if it appears that the value of their holdings will decline, as like in a bear market (which we are still in) they might be encouraged to lighten the amount of leverage they have. So the threat of the repealing of the tax relief programs that are in place *COULD* cause people to sell their high-end homes at a loss. It all depends on the amount of leverage they are using to maintain their lifestyles.