Even if no filtering is configured, when the delay option is different than 0 navigation between the items in the DropDownList does not work correctly.
The correct item is not always selected. In the demo, no delay is configured, but the default value is 500. The delay is supposed to affect the DropDownList only when filtering is enabled.
Note: Currently, when the filter option is configured, changing selection without opening the DropDownList is not possible.
Set delay to 0 - Dojo
The selection of the items should be correctly changed when typing, even if a delay different than 0 is configured.
Also, it should be possible to change the selected item by typing in the keyboard even if the filter option is set and the DropDownList is closed.