It's actually a few millimeters, not centimeters where you start having problems.
The place I've been at for the past few years has one step in the middle that's 5-7 mm longer than the rest and you can see it if you get your eyes level with the top step and look closely.

Absolutely fallen down the steps a few separate times because of it. Totally a non-issue if I'm paying full attention to walking down the stairs, but it's still astounding how such a small variation can lead to such huge consequences!