Earlier quoted context omitted.
Well, that certainly selects for engineers willing to do unreasonable amounts of work without questioning it.
If that's how you want to test potential engineers, I don't necessarily see a problem with the task itself. Just pay them! I'm sure Uber can find the budget for that.
If you want to limit your pool of potential hires to rock stars who don't have jobs (pool size of approx. zero) this is a great approach.