Darker single color gradients exhibit very strongly noticeable color stairs. Tried to generate one for a background, locked horrible. It only looked good once I randomized the gradients a bit, i.e., even with 8 bit colors, you might need dithering.
Similar effects can be noticed in relatively dark photos of scenes with gradients, e.g., a sky.
Of course my experience is only 1 test point...
Yes, if you actually compare a 10-bit and an 8-bit panel next to another, it's immediately obvious.
Here's a photo of a 6-bit, 10-bit and 8-bit gradient on a native 10-bit panel without any dithering (Dell UP2718Q): https://i.k8r.eu/VolYbQ.png
Running on a Dell UP2718Q, in HDR10 mode.
That said, in person can be – depending on environmental lighting conditions – much more subtle. The test here was done with blinds closed in a mostly dark room.
In bright environments 8-bit is enough, and 6-bit with dithering can be close, but in dark environments (such as when watching a movie or gaming) you'll even notice banding in 10-bit content.