What
In lists where you pick an option with the keyboard, such as settings menus, the PageUp and PageDown keys are now bound to move a page up and a page down. These keyboard actions are named select:pageUp and select:pageDown.
Why
Long lists can be moved through a page at a time instead of one line at a time.
Names in the bundleselect:pageUpselect:pageDown
Documented inclaude-code/keybindings
Something disagreesSomething we can check disagrees with this entry, or the writer said they could not settle it.
The writer flagged doubt
It is not confirmed that every selection list acts on these two keys.