system
A chat on subreddit /r/wallstreetbets
human
Some places give you your entire allotment of shares on day one, but they only vest 20% per year for the first 5 years. Apparently the sale of the company triggered the 100% vesting immediately for him.

gpt
What a bizarre cash-flow for the company.  Guess it's the same to the employee in the end anyway unless they leave early.