There is loads of UI consistent inconsistency, where you can/cannot navigate the UI with arrow keys is completely random:

- search screen, you can navigate it all with up/down arrow keys (but not left/right)
- start menu, you can use both up/down/left/right in some areas, in another area only left/right and you can _mostly_ only switch sections with tab
- lock screen, you can only navigate with tab, no arrow keys. Until that is you open the power menu, then you can navigate with only up/down and you can't tab out of the menu, you need to use escape for that

It feels like the different teams for different (but adjacent) areas of the UI never used the other features...