No one has to sell. That part is optional. This allows employees and former employees to receive shares and to pay the taxes due on receipt. Paying taxes at low valuation is a win.
> Forced to sell at a 50% discount (if they want liquidity)
Obviously no one is literally forced to sell. Is this really that hard to understand? This entire thread is about how by not going IPO, the employees were unable to sell. I'm sure they would have preferred to sell a few years ago instead of paying less taxes now.
It also seems that some employees' options are expiring, so while they aren't literally forced to sell, in reality, they are.
That's true but the reality for many will be selling at least the amount of shares to cover the cost of executing their options. And because the next window to sell could be undetermined (possibly many years in the future), many employees will find it prudent to get liquidity that would cover their cash needs for the next fair-number-of-years. (Based on their understanding of what their stake is worth now. Of course they're going to have that number in mind even if it wasn't able to be realized until now...)