If an employee periodically vests a fixed number of shares, as opposed to a fixed dollar amount of shares, this is actually untrue.

Assume an employee's marginal tax rate is 40% and their capital gains rate is 15%. Then there are 2 scenarios:

1. Vest 100 shares at $100 apiece. After tax that's 60 shares * $100 = $6000 total.

2. A sudden price drop causes 100 shares to vest at $50. After tax that's 60 shares * $50 = $3000. Later the price rises to $100 and the employee sells them. Another $3000 in capital gains, leaving $2550 after taxes. Total = $5250.