A large number of big tech companies have had unusual retention initiatives, including Robinhood issuing ad-hoc stock grants after a stock drop, Apple issuing $180k stock grants out of cycle and others.
Apple was considered on the lower end of FAANG-tier salaries, so the grants which were outside of the normal process are unusual.
This isn't an isolated incident. Even companies that pay mid-tier salaries ($300-350k for a senior in the Bay Area) are experiencing above normal attrition.
Attrition is a real problem right now. Hiring is fierce. If you're a senior or staff level engineer, it's a buyer's market.