They make it clear that Amazon prefer employees who'll stay there for a while because employees only become value after a couple of years, or if you're feeling less generous, Amazon know that they'll extract all the value from someone in under a year before they're driven out. Either way the terms aren't insane; they're just very much weighted to the employer's beliefs.
You're right. I should have finished that thought with "compared to a standard 1-year cliff and 25% per year".
In any case, dragging relocation out over two years feels wrong to me given that relocation is binary. I suppose in effect they are using it as a way to attach strings to a signing bonus.
