Disclaimer: Ex-Amazonian, so discount as you see fit based on whatever brainwashing you might assume I’ve been subjected to ;)
The rear weighted AMZN approach made sense to me in terms of both optimising retention and some proxy for reward to contribution. I say this also as someone who left after 2 years and as a result left most of their stock unvested. It definitely made the choice to leave much harder so I’d expect it to skew more heavily toward retention benefits than a typical schedule. A typical schedule has a linear growth of what you’ve vested. I’d expect the value of contribution of a person to grow over time though. More context, more experience, more everything. Hopefully that means the you 3 years from now is making a more significant contribution than the you they hired. Typical schedules hope that the increase in valuation accounts for that compounding return. AMZN have shifted it to the vesting schedule.
That said they always talk about “total compensation”. So for the stock you’re not getting in the first two years you typically get as cash via a “hiring bonus” anyway. You could always just use that cash to go buy the equivalent amount in stock, no vesting required.