It's fairly straightforward but widely misunderstood (or misapplied), hence the level of cynicism in these comments. Every level carries with it a certain set of expectations. Once you get promoted, you're now subject to those expectations. If I, as your manager, promote you to the next level without having evidence of your ability to perform at the next level, and you then bomb, it's bad news for everyone. For you (you get a bad review after previously doing quite well presumably), for your peers (they're seeing someone promoted above their ability, potentially impacting others around), and for me (it's my failure as a manager). There's always going to be some amount of luck involved in whether a promotion is successful or not, and it's my job as your manager to derisk it as much as possible. Doing your job at your level well is only evidence of just that, there needs to be some consistency of operating at the next level to the extent reasonable.

To be clear, I'm not saying you should be working extra hours to do this. If that's required, either your manager is not reasonable or you're likely not there yet and if I were to promote you, you might burn out soon.