These stories scare me. Particularly from Amazon where you don't get most of your TC until year 3. At least at Netflix they pay more cash and if I get fired after a year I have it in my bank.
You can think about it this way. When you join, Amazon takes part of the money they need to pay you in year 3 & 4 and buy with it Amazon stock which you can sell only in year 3 & 4. (one difference is that you pay income tax on it when you receive it and not capital gain tax)