Earlier quoted context omitted.
In this case it is free arbitrage. This is because if the stock goes way down, and you are 1 year into your 4 year vest, then you can leave the company, and get a high compensation package somewhere else. Do you understand how this makes it so you have free downside protection, from those other 3 years, because you can leave and get the high salary somewhere else, if the stock crashes?
High package elsewhere is not free money... Also leaving the company isn’t free (you lose unvested shares, atleast). this isn’t arbitrage. even arbitrage usually has some carrying risk in between the two transactions.
Never mind, see sibling threads.