This sort of vesting schedule is pretty common. I'm not sure busting Amazon's balls on this one is very genuine.
How about this other aspect of their 401k plan? I have never worked at a company that does that. Being so closely tied to your place of work financially is usually not recommended.
Demand more.
Well-funded 401k matching plans that vest immediately certainly help with mobility, for those who care to stick around for the match!
I mean, it does suck, but it is what one sign for, so no amount complaining later will change that